UNIVERSITY  OF  CALIFORNIA  PUBLICATIONS 

COLLEGE  OF  AGRICULTURE 

AGRICULTURAL  EXPERIMENT  STATION 

BERKELEY,  CALIFORNIA 


THE  RELATIVE  COST  OF  YARDING 
SMALL  AND  LARGE  TIMBER 


BY 

DONALD  BRUCE 


BULLETIN  No.  371 

October,  1923 


UNIVERSITY  OF  CALIFORNIA  PRESS 

BERKELEY 

1923 


Digitized  by  the  Internet  Archive 

in  2012  with  funding  from 

University  of  California,  Davis  Libraries 


http://www.archive.org/details/relativecostofya371bruc 


THE  RELATIVE  COST  OF  YARDING 
SMALL  AND  LARGE  TIMBER 

By  DONALD  BEUCE 


In  an  investigation  of  the  relative  cost  of  making  logs  from  small 
and  large  timber  (described  in  a  previous  bulletin1  of  this  series),  it 
was  shown  that  it  costs  three  times  as  much  per  m.b.m.  to  make  logs 
from  18 -inch  as  from  48 -inch  trees,  and  that  below  that  diameter  the 
costs  undoubtedly  rise  rapidly  with  each  further  decrease  in  size.    In 


*6 


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b-b 

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16    20    ZZ    Z4    Z6    28    30    32    34-  36    38    40    4Z 
Tree,  d/ameter  breast ■  hiqh  —  inches 


44  46  48 


Fig.  1. — Influence  of  tree  diameter  on  cost  per  M.B.M.  of  yarding  in  three 
localities,  showing  relatively  high  cost  for  small  trees. 

the  following  pages  are  given  the  results  of  similar  studies  of  the  cost 
of  yarding  with  steam  donkey  engines.  These  investigations  included 
the  detailed  timing  by  stop  watch  of  the  handling  of  every  log  on 
two  complete  settings  and  on  an  additional  half  setting.  Although 
two  of  these  three  studies  were  located  in  conditions  representative 
of  the  east  side  of  the  Sierra  and  the  other  in  those  typical  of  the 
west  side,  and  although  the  organization  of  the  yarding  crew  and  its 
equipment  were  similar  in  no  two  instances,  yet  in  all  three  studies 
it  was  found  that  it  costs  from  five  to  eight  times  as  much  per  m.b.m 
to  yard  logs  from  18-inch  as  those  from  48-inch  trees  and  that  for 
trees  below  18  inches  in  diameter  costs  are  undoubtedly  even  higher. 

i  Bruce,  Donald,  "The  Relative  Cost  of  Making  Logs  from  Small  and  Large 
Timber,"  Bulletin  339,  University  of  California  Agricultural  Experiment 
Station,  January,  1922. 


4  UNIVERSITY    OF    CALIFORNIA— EXPERIMENT    STATION 

Table  1  and  figure  1  summarize  these  results.  The  similarity  in 
form  of  the  three  curves  in  the  figure  is  striking;  and  the  ratios 
between  the  highest  and  lowest  of  each  of  the  three  sets  of  values  as 
shown  in  the  table  differ  little.  Tn  Study  A,  the  18-inch  trees  cost 
7.8  times  as  much  per  m.b.m.  to  yard  as  did  the  48-inch  trees,  in 

TABLE  1 
Influence  of  Tree  Diameter  on  Cost  of  Yarding  Labor 


Diam- 

Cost  per  M.  B.  M.,  G 

ross  Scale 

breast 

Study  B 

Study  C 

high, 

Study  A 

Average 

inches 

Yarder 

Swing 

Total 

Yarder 

Swing 

Total 

18 

$5.38 

$4.27 

$1.55 

$5.82 

$3.38 

$1.88 

$5.26 

$5.49 

20 

3.16 

2.45 

.94 

3.39 

2.65 

1.45 

4.10 

3.55 

22 

2.09 

1.69 

.69 

2.38 

2.01 

1.17 

3.18 

2.55 

24 

1.69 

1.25 

.55 

1.80 

1.56 

.92 

2.48 

1.99 

26 

1.36 

1.00 

.46 

1.46 

1.27 

.78 

2.05 

1.62 

28 

1.15 

.85 

.41 

1.26 

1.09 

.68 

1.77 

1.39 

30 

1.04 

.75 

.37 

1.12 

.98 

.61 

1.59 

1.25 

32 

.97 

.69 

.34 

1.03 

.91 

.56 

1.47 

1.16 

34 

.92 

.64 

.33 

.97 

.85 

.54 

1.39 

1.09 

36 

.86 

.62 

.31 

.93 

.81 

.50 

1.31 

1.03 

38 

.83 

.60 

.30 

.90 

.78 

.48 

1.26 

1.00 

40 

.78 

.59 

.29 

.88 

.75 

.47 

1.22 

.96 

42 

.76 

.58 

.28 

.86 

.71 

.46 

1.17 

.93 

44 

.72 

.57 

.27 

.84 

.68 

.45 

1.13 

.90 

46 

.70 

.56 

.27 

.83 

.65 

.44 

1.09 

.87 

48 

.69 

.55 

.26 

.81 

.62 

.44 

1.06 

.85 

Wage  scale  used:  Per  hour 

Hooktender   : $.85 

Engineer  67% 

Fireman    47% 

Woodbuck 45 

Rigger,  head .60 

Rigger,  assistant,  chaser,  frogger,  chute  tender 55 

Unhooker 55 

Choker  hole  digger,  frog  shoveler 45 

Whistle  punk 40 

Teamster 55 

Horse 25 

Crew  cost  per  minute:   Study  A,  $.11.5;   Study  B,  yarder,   $.109; 
swing,  $.051;  Study  C,  yarder,  $.102;  swing,  $.067. 


Study  B,  7.2,  and  in  Study  C,  5.0,  with  an  average  of  6.5  times  as 
much.  No  figures  were  available  for  trees  under  18  inches  in  diameter 
since  trees  smaller  than  this  were  seldom  yarded,  but  the  trend  of 
the  curves  is  convincing  evidence  that  even  higher  costs  would  be 
encountered  for  these  smaller  sizes.  It  is  to  be  noted,  of  course,  that 
machinery,  rigging,  and  crew  organization  were  all  designed  to 
handle  large  timber  and  that  no  definite  conclusions  can  be  drawn 
from  the  present  study  applicable  to  stands  consisting  wholly,   or 


Bulletin  371 J       the  relative  cost  of  yarding  timber  5 

almost  wholly,  of  very  small  trees  and  yarded  with  machinery 
appropriate  thereto. 

The  costs  given  are  for  labor  only,  without  any  allowance  for 
depreciation,  renewals,  or  maintenance  of  equipment.  The  inclusion 
of  such  items  would,  of  course,  increase  all  the  costs,  but  there  is  no 
reason  to  suppose  that  it  would  affect  materially  the  relations  between 
the  costs  for  trees  of  different  sizes. 

The  rapid  fluctuations  of  wage  scales  during-  the  past  few  years 
have  made  cost  figures  in  dollars  and  cents  misleading.  Throughout 
this  study,  therefore,  all  costs  have  been  reckoned  in  minutes  of  time 
spent  by  the  yarding  crew,  with  the  exception  of  table  1,  in  which 
time  was  translated  into  money  at  an  assumed  scale  of  wages  (stated 
in  the  table)  which  is  fairly  representative  of  1923  conditions. 

The  data  obtained  in  each  study  will  now  be  described,  with  an 
explanation  of  how  the  conclusions  have  been  reached.  Each  study 
will  be  treated  separately,  the  first  in  order  being  outlined  in  con- 
siderable detail,  while  the  others,  similar  in  technique,  will  be  more 
briefly  summarized. 

All  three  studies  were  made  in  cooperation  with  representative 
lumber  companies  of  the  Sierra  Nevada  region  under  an  agreement 
that  the  identity  of  the  companies  would  not  be  disclosed.  The  studies 
will  therefore  be  referred  to  as  Study  A,  Study  B,  and  Study  C, 
respectively. 

STUDY  A 

This  study  was  located  under  conditions  typical  of  the  better 
portions  of  the  east  side  of  the  Sierra.  The  topography  was  gentle 
(as  shown  in  the  map  of  figure  2),  the  ground  sloping  gradually  away 
from  the  railroad  track,  thus  offering  an  almost  ideal  yarding  chance. 
The  timber  was  about  80  per  cent  western  yellow  pine  and  Jeffrey 
pine  ("California  White  Pine")  and  20  per  cent  white  fir.  The  stand 
per  acre  averaged  about  44  m.b.m.2  (on  the  area  actually  yarded), 
an  unusually  heavy  stand  for  this  region. 

The  study  covered  a  half  setting  only,  or  about  13.3  acres,  the 
yarder  remaining  in  one  position  (except  for  a  slight  shift  on  account 
of  an  interference  of  its  line  with  the  steam  saw)  throughout  the 
period  of  observation.  The  yarder  was  a  10  by  11  simple-geared 
wide-drum  machine  manufactured  by  the  Willamette  Iron  and  Steel 
Works.  The  lead  of  the  line  was  through  a  bull  block  hung  near  the 
ground.     The  logs  were  all  hauled  in  long  lengths  and  were  bucked 


2  This  is  by  the  Scribner  log  rule,  which  is  used  throughout  this  bulletin. 


6 


UNIVERSITY    OF    CALIFORNIA — EXPERIMENT    STATION 


into  short  lengths  (averaging  about  16  feet)  by  a  steam  saw  in  a 
short  chute  at  the  landing.  Since  only  one  engine  was  used,  the 
spotting  of  the  logs  for  the  steam  saw  was  done  by  the  yarder.  Logs 
were  generally  handled  one  at  a  time,  although  occasionally  where  it 
was  particularly  convenient  to  do  so,  two  were  taken  at  a  single  trip. 
The  average  load  per  trip  was  116-1  feet  b.m.  The  yarding  of  the 
area  required  nine  working  days.  The  location  of  the  railroad,  land- 
ing, bucking  chute,  yarder,  and  the  various  positions  of  the  main  line 
are  shown  in  figure  2. 


Fig.  2. — Contour  map  of  yarding  area  of  Study  A,  showing  (A)  railroad, 
(B)  landing,  (C)  bucking  chute,  (D)  position  of  yarder,  and  the  positions  of 
the  yarding  line. 


The  crew  employed  was  as  follows : 


1  hooktender 
1  engineer 
1  fireman 
1  wood  buck 
3  risers 


1  chaser 

1  frogger 

1  chute  tender 

1  choker  hole  digger 

1  whistle  punk 


In  addition  a  horse  was  used  for  changing  line,  the  yarder  not  being 
equipped  with  a  straw  line.  The  fuel  burned  by  the  donkey  consisted 
of  mill  refuse,  the  value  of  which  was  not  included  in  the  operating 
cost. 


BULLETIN  371]         THE  RELATIVE  COST  OF  YARDING  TIMBER 


Description  of  Data  Collected 

The  data  collected  consisted  of  stop  watch  observations  of  each  trip 
made  by  the  yarder  and  a  measurement  and  scale  of  the  logs  yarded. 
This  information  was  obtained  by  two  observers,  one  stationed  at  the 
landing  and  the  other  near  the  outer  end  of  the  yarding  line.  The 
stop  watches  used  were  graduated  in  minutes  and  hundredths  of 
minutes  to  facilitate  computations.  The  subdivisions  of  time  recorded 
were  as  follows: 

' '  Out ' ' :  The  return  of  the  main  line  to  the  position  of  the  log  next 
to  be  hauled. 

"Shift":   Movements  of  the  main  line  (after  the  "out")  for  the 
explicit   purpose   of   leaving   a    choker    at   a   desired   point. 
" Shifts"  were  often  avoided  by  carrying  the  chokers  by  hand 
from  the  end  position  of  the  out. 

"Taking  off  choker" :  "Removal  of  empty  choker  in  connection  with 
a  " shift" — usually  occurring  between  the  "out"  and  the 
"shift." 

"Hook":  Connecting  the  choker  to  the  line,  measured  from  the 
end  of  the  "out"  or  "shift"  until  the  line  was  under  tension 
for  the  trip  in. 

"  In " :  The  hauling  of  the  log  to  the  landing,  measured  from  the 
end  of  the  "hook"  until  the  engine  stops.  This  item  was 
usually  divided  into  two  or  more  parts  by  the  "block." 

"Block":  Unhooking  the  choker,  passing  it  around  the  bull  block 
and  hooking  it  to  the  line  again ;  measured  from  the  time  the 
engine  stopped  until  the  line  was  once  more  under  tension, 
but  with  minor  engine  movements  to  assist  in  this  operation 
included  therein. 

"Spotting":  Engine  movements  for  the  purpose  of  placing  logs 
in  the  chute  in  convenient  position  for  bucking  into  short 
lengths. 

"Unhook":  The  release  of  the  choker  from  the  log  or  sometimes 
of  the  choker  from  the  line  and  the  placing  of  an  empty  choker 
or  chokers  on  the  line;  measured  from  the  end  of  the  "in"  to 
the  beginning  of  the  "out." 

"Delays":  The  cause  of  each  delay  was  identified  and  noted. 
Delay  items  were  later  grouped  into  those  essentially  connected 
with  the  ' '  out ' '  (hereafter  called  ' '  out  delays " ) ,  the  "  in, "  etc., 
and  those  which  cannot  be  thus  associated  with  any  of  the  above 
items  and  hence  must  be  classed  as  "general  delays."  For 
example  :  the  hanging  up  of  a  log  on  a  stump  is  an  "  in  delay ' ' ; 
the  loss  of  a  choker  from  the  line  during  the  "out"  is  an  "out 
delay,"  while  the  time  occupied  in  changing  the  positions  of 
the  lines  or  repairing  the  blocks  is  ' '  general  delay. ' ' 


8 


UNIVERSITY    OF    CALIFORNIA— EXPERIMENT    STATION 


Table  2  is  a  summary  of  the  results  obtained  and  shows  for  each 
of  the  above  items  the  average  time  per  trip,  the  per  cent  of  the  total 
time,  and  the  average  time  per  occurrence. 

TABLE  2 

Distribution  of  Time  between  Operations  Involved  in  Yarding 

STUDY  A 


Operation 


Out  inside  of  bull  block 

Out  outside  of  bull  block 

Total  out 

Shift 

Taking  off  choker 

Hook 

Total  time  between  out  and  in 

In  outside  of  bull  block 

In  inside  of  bull  block 

Total  in 

Block. 

Spotting 

Unhook 

Total  time  between  in  and  out 

Delays — Out 

Choker  dropped 

Choker  fouled  in  bull  block 

Miscellaneous 

Delays — In 

Hung  up  on  stumps,  trees,  logs  and 
slash 

Avoiding  stumps,  trees,  logs  and  slash 

Chute  trouble 

Miscellaneous : 

Delays — Spotting 

Waiting  for  steam  saw 

Delays — General 

Changing  line 

Stopping  early  at  noon  or  night 

Engine  trouble 

Repairing  lines,  blocks,  etc 

Shifting  donkey  engine 

Miscellaneous 

Total  delays 

Total  time  per  trip 


Average  time 

per  trip — 

minutes 


.29 

.72 

.16 

.27 
.57 

1.23 
.53 

.93 

1.19 

.81 


.06 
.02 
.05 


.61 
.22 
.33 
.31 

.27 

.64 
.17 

.09 
.11 

.08 

.27 


1.01 


1.00 


1.76 
.93 


2.00 


3.23 


9.93 


Per  cent  of 
total 
time 


2.9 
7.3 

1.6 

2.7 
5.8 

12.4 
5.3 

9.4 
12.0 

8.1 


0.6 
0.2 
0.5 


6.2 
2.2 
3.3 
3.1 

2.7 


10.2 


10.1 


17.7 
9.4 


20.1 


32.5 
100.0 


Average  time 

per 

occurrence — 

minutes 


.29 

.72 

.21 
.36 
.55 

.79 
.53 
.32 
.60 
.25 
.81 


.54 
.56 


1.95 
1.09 
1.50 


1.59 

12.30 
6.34 
4.03 
4.93 

40.13 


The  reason  for  this  last  column  is  that  a  number  of  items  occurred 
but  rarely,  instead  of  regularly  once  per  trip  (for  example,  changing 
the  position  of  the  line),  and  that  it  is  of  interest  to  know  not  only 
what  proportion  of  the  entire  time  cost  may  be  attributed  to  such  an 
item  but  also  the  average  time  required  therefor  when  it  occurred. 


Bulletin  371]       THe  relative  COST  of  yarding  timber 


Influence  on  Time  of  Variations  in  Distance  which  Log  is  Hauled 

Since  the  size  of  the  log  which  was  hauled  during  each  trip  of  the 
line  was  recorded,  it  would  have  been  a  simple  matter  to  obtain  the 
average  time  required  in  the  case  of  logs  of  various  sizes  for  each  of 
the  above  items  and  for  the  trip  as  a  whole.  The  resulting  figures 
might  not  reflect  accurately,  however,  the  influence  of  log  size  on  time 
and  hence  on  cost,  because  there  is  a  possibility  that  variations  in  the 
distances  hauled  might  have  distorted  their  interrelations.  It  is  not 
improbable,  particularly  in  view  of  the  patchy  distribution  of  the 
stand,  that  the  large  logs  may  have  been  hauled  on  the  average  a 
shorter  distance  than  the  small,  or  vice  versa.  It  is  therefore  neces- 
sary to  determine  first  the  influence  of  variations  in  distance  on  the 
several  time  factors  so  that  for  such  variations  suitable  allowances  can 
be  made. 

This  analysis  can  be  simplified  by  segregating  the  various  time 
items  into  three  groups :  ( 1 )  those  which  vary  with  distance ;  ( 2 )  those 
which  are  independent  of  distance  and  which,  while  variable  on 
account  of  accidental  causes,  may  be  treated  as  a  constant  in  the 
average  trip;  (3)  those  which  constitute  a  ''time  overhead"  properly 
to  be  pro-rated  against  the  total  of  the  first  two  groups.  In  the  first 
group  fall  the  following : 

"Out"  outside  of  bull  block  72  minutes  per  trip 

"In"  outside  of  bull  block 1.23  minutes  per  trip 

"Out  delays"  outside  of  bull  block 11  minutes  per  trip 

"In  delays"  outside  of  bull  block 1.05  minutes  per  trip 

Total  of  items  varying  with  distance 3.11  minutes  per  trip 

In  the  second  group  fall  the  following : 

"Out"  inside  of  bull  block 29  minutes  per  trip 

"Shift"    16  minutes  per  trip 

"Taking  off  choker"  27  minutes  per  trip 

"Hook" 57  minutes  per  trip 

"In"  inside  of  bull  block 53  minutes  per  trip 

"Block" 93  minutes  per  trip 

"Spotting"    1.19  minutes  per  trip 

"Unhook" .81  minutes  per  trip 

"Out  delays"  occurring  inside  of  bull  block 02  miuutes  per  trip 

"In  delays"  occurring  inside  of  bull  block 42  minutes  per  trip 

"Spotting  delays"  27  minutes  per  trip 

Total  of  items  independent  of  distance 5.46  minutes  per  trip 

In  the  third  class  fall  the  "general  delays"  amounting  to  1.36  minutes 
per  trip. 


10 


UNIVERSITY    OF    CALIFORNIA EXPERIMENT    STATION 


To  analyze  the  four  items  in  the  first  of  these  groups,  the  trips 
were  segregated  into  distance  classes  and  the  average  "in,"  "out," 
"in  delay,"  and  "out  delay"  for  each  distance  was  obtained.  The 
results,  as  adjusted  graphically  by  means  of  curves  to  give  regular 
progressions  in  the  values,  are  shown  in  table  3.  The  decrease  of 
the  "out  delay"  time  as  the  distance  increases  is  probably  purely 
accidental,  for  in  the  other  two  studies  the  trend  is  in  the  opposite 
sense.    The  other  items  and  the  total,  all  increase  as  would  be  expected, 


TABLE  3 

Influence  of  Variations  in  Distance  on  Yarding  Items  Directly 
Affected  Thereby 

STUDY  A 


Time  per  trip,  minutes 

"Diet  onnp 

lylolallUU) 

feet 

"Out" 

"Out  delay" 

"In" 

"In  delay" 

Total 

50 

.14 

.37 

.21 

.18 

.90 

100 

.24 

.30 

.39 

.34 

1.28 

150 

.32 

.25 

.54 

.48 

1.59 

200 

.39 

.21 

.66 

.58 

1.84 

250 

.44 

.18 

.75 

.66 

2.03 

300 

.50 

.15 

.83 

.73 

2.21 

350 

.55 

.13 

.91 

.81 

2.40 

400 

.61 

.11 

1.00 

.88 

2.60 

450 

.66 

.10 

1.08 

.96 

2.80 

500 

.71 

.09 

1.18 

1.04 

3.02 

550 

.76 

.09 

1.28 

1.14 

3.27 

600 

.82 

.08 

1.40 

1.24 

3.54 

650 

.87' 

.08 

1.52 

1.34 

3.81 

700 

.94 

.07 

1.66 

1.46 

4.13 

750 

1.00 

.07 

1.82 

1.60 

4.49 

800 

1.07 

.07 

1.96 

1.73 

4.83 

850 

1.15 

.06 

2.14 

1.89 

5.24 

900 

1.24 

.06 

2.33 

2.05 

5.68 

although  not  in  the  same  proportion  as  the  distance.  Increasing  the 
distance  nine  times  increases  the  time  less  than  five  times. 

The  average  total  time  required  for  a  trip  of  any  given  distance  is 
the  sum  of  that  stated  in  table  3  plus  the  total  of  the  items  independent 
of  distance,  or  5.46  minutes  (see  page  9),  plus  the  proper  share  of 
the  "general  delays."  Since  this  latter  item  amounts  to  1.36  minutes 
per  trip  out  of  a  total  of  9.93  minutes,  it  constitutes  15.9  per  cent  of 

1  ^fi 
the  sum  of  the  items  other  than  general  delays :  *' — — —  =  .159 

o.Jo  l.OO 

This  percentage  may  accordingly  be  used  as  a  pro-rating  coefficient 
to  distribute  the  "general  delay"  item.  These  computations  and 
the  resulting  total  time  per  trip  are  given  in  table  4. 


BULLETIN  371]         THE  RELATIVE  COST  OF  YARDING  TIMBER 


11 


Influence  on  Time  of  Variations  in  Size  of  Log 

It  is  now  possible  to  investigate  the  influence  of  log  size  on  cost. 
The  most  practicable  measure  of  log  size  is  the  gross  scale,  since  any 
defective  portions  of  a  log  will  weigh  nearly  as  much  as  though  they 
were  sound.  The  available  trips  were  therefore  re-classified  by  the 
gross  volume  hauled,  each  class  comprising  a  range  of  100  feet  b.m. 


TABLE  4 
Influence  of  Variations  in  Distance  on  Total  Time  of  Yarding  per  Trip 

STUDY  A 


Time  per  trip,  minutes 

A 

B 

A+B 

1.159x(A+B) 

Distance 

Time  of  items 

Average  time  of 

Sum  of  all  items 

Total 

yarded, 

directly 

items 

except 

including 

feet 

affected 

independent  of 

general 

general 

by  distance 

distance 

delays 

delays 

50 

.90 

5.46 

6.36 

7.37 

100 

1.28 

5.46 

6.74 

7.81 

150 

1.59 

5.46 

7.05 

8.17 

200 

1.84 

5.46 

7.30 

8.45 

250 

2.03 

5.46 

7.49 

8.68 

300 

2.22 

5.46 

7.68 

8.89 

350 

2.40 

5.46 

7.86 

9.11 

400 

2.60 

5.46 

8.06 

9.35 

450 

2.80 

5.46 

8.26 

9.57 

500 

3.02 

5.46 

8.48 

9.83 

550 

3.27 

5.46 

8.73 

10.12 

600 

3.55 

5.46 

9.01 

10.43 

650 

3.81 

5.46 

9.27 

10.74 

700 

4.13 

5.46 

9.59 

11.11 

750 

4.50 

5.46 

9.96 

11.54 

800 

4.83 

5.46 

10.29 

11.92 

850 

5.24 

5.46 

10.70 

12.39 

900 

5.68 

5.46 

11.14 

12.91 

It  is  obvious  that  many  items,  such  as  "out"  and  "out  delays," 
will  be  entirely  independent  of  the  load  hauled.  There  are  in  fact 
but  five  which  are  correlated  therewith,  i.e.,  "in  outside  of  the  bull 
block,  "in  delays"  outside  of  the  bull  block,  "hook,"  "in"  inside 
of  the  bull  block,  and  "in  delays"  inside  of  the  bull  block.  The  first 
two  of  these  are  items  affected  by  the  distance  hauled,  while  the 
remaining  three  are  not.  The  latter  can  therefore  be  analyzed 
directly  by  computing  the  average  time  of  each  for  the  various  size 
classes  and  graphically  readjusting  the  averages  by  means  of  curves. 
The  resulting  values  are  given  in  the  last  three  columns  of  table  5. 
In  the  case  of  the  former  items,  however,  the  values  must  be  dis- 
counted for  the  actual  average  distances  hauled.     This  has  been  done 


12 


UNIVERSITY    OF    CALIFORNIA — EXPERIMENT    STATION 


by  entering  in  the  second  and  third  columns  of  the  same  table  the 
average  percentage  ratio  between  the  actual  time  for  each  log  in  a 
given  size  class  and  the  average  time  for  the  corresponding  distance. 
To  find  the  average  "in"  time  for  a  log  of  given  size  hauled  a  given 

TABLE  5 

Influence  of  Variations  in  Size  of  Log  on  Yarding  Times  Affected  Thereby 

STUDY  A 


Volume  of 
log,  gross 

scale, 
Scribner, 
feet,  b.m. 

"In"  (outside 

of  bull 

block), 
per  cent  of 

average 

time  for 
corresponding 

distance 

"In  delay" 

outside  of 

bull  block, 

per  cent  of 

average 

time  for 

corresponding 

distance 

"Hook," 
minutes 

"In"  inside 
of  bull 
block, 
minutes 

"In  delay" 
inside  of 

bull  block, 
minutes 

100 

86.5 

38. 

.50 

.42 

.19 

200 

89.0 

40. 

.51 

.42 

.20 

300 

90.8 

42. 

.51 

.43 

.22 

400 

92.5 

44. 

.51 

.44 

.23 

500 

94.0 

46. 

.51 

.44 

.25 

600 

96.0 

48. 

.52 

.45 

.26 

700 

97.0 

52. 

.52 

.46 

.27 

800 

98.5 

56. 

.52 

.46 

.28 

900 

99.7 

60. 

.53 

.47 

.30 

1000 

100.8 

66. 

.53 

.48 

.31 

1100 

101.5 

72. 

.54 

.49 

.33 

1200 

102.7 

78. 

.54 

.49 

.34 

1300 

103.5 

88. 

.55 

.50 

.35 

1400 

104.0 

98. 

.56 

.51 

.37 

1500 

104.6 

108. 

.56 

.51 

.38 

1600 

105.2 

122. 

.57 

.52 

.40 

1700 

105.9 

136. 

.58 

.53 

.41 

1800 

106.3 

152. 

.59 

.53 

.42 

1900 

107.0 

168. 

.60 

.54 

.44 

2000 

107.3 

184. 

.61 

.55 

.47 

2100 

107.6 

204. 

.62 

.55 

.52 

2200 

108.0 

218. 

.64 

.56 

.57 

2300 

108.3 

236. 

.66 

.57 

.66 

2400 

108.5 

250. 

.68 

.58 

.75 

2500 

108.8 

264. 

.70 

.58 

.83 

2600 

109.0 

278. 

.72 

.59 

.92 

2700 

109.2 

290. 

.74 

.60 

1.01 

2800 

109.5 

298. 

.76 

.60 

1.09 

2900 

109.8 

306. 

.78 

.61 

1.18 

3000 

110.0 

316. 

.81 

.62 

1.27 

distance,  it  would  then  be  necessary  to  select  from  column  4  of  table  3 
the  "in"  time  corresponding  to  the  distance  and  multiply  it  by  the 
percentage  correction  from  column  2  of  table  5  corresponding  to  the 
size  class. 

The  effect  of  log  size  on  the  items  listed  in  this  table  is  remark- 
ably small.    Only  the  two  delay  items  are  at  all  sensitive  to  variations 


Bulletin  371]       the  relative  COST  OF  yarding  timber 


13 


therein.  Large  logs  cost  more  to  handle  than  small,  but  the  increase 
in  cost  is  far  from  proportionate  to  the  increase  in  volume.  It  is 
obvious  that  since  log  size  affects  differently  the  several  details  that 
go  to  make  up  yarding  time,  its  effect  on  the  total  yarding  time  will 

TABLE  6 

Influence  of  Variations  in  Size  of  Log  on  Total  Yarding  Time  per  Trip 
for  Different  Distances 

STUDY  A 


Volume 

of  log, 

gross  scale, 

Total  time  of  trip, 

Time  cost  .per  M.B.M.,  gross, 

minutes 

minutes 

Distance  in  feet 

Distance  in  feet 

Scribner, 
feet,  b.m. 

100 

500 

900 

100 

500 

900 

100 

7.02 

8.43 

10.61 

70.2 

83.4 

106.1 

200 

7.07 

8.51 

10.75 

35.3 

42.5 

53.7 

300 

7.12 

8.59 

10.87 

23.7 

28.6 

36.2 

400 

7.16 

8.66 

10.99 

17.9 

21.4 

27.5 

500 

7.20 

8.73 

11.10 

14.4 

17.5 

22.2 

600 

7.25 

8.81 

11.23 

12.1 

14.7 

18.7 

700 

7.30 

8.90 

11.39 

10.4 

12.7 

16.3 

800 

7.35 

8.99 

11.55 

9.2 

11.2 

14.4 

900 

7.40 

9.09 

11.70 

8.2 

10.1 

13.0 

1000 

7.46 

9.21 

11.91 

7.5 

9.2 

11.9 

1100 

7.51 

9.32 

12.10 

6.8 

8.6 

11.0 

1200 

7.57 

9.44 

12.30 

6.3 

7.9 

10.2 

1300 

7.65 

9.60 

12.59 

5.9 

7.4 

9.7 

1400 

7.72 

9.77 

12.88 

5.5 

7.0 

9.2 

1500 

7.80 

9.92 

13.16 

5.2 

6.6 

8.8 

1600 

7.88 

10.13 

13.54 

4.9 

6.3 

8.5 

1700 

7.98 

10.35 

13.92 

4.7 

6.1 

8.2 

1800 

8.08 

10.58 

14.35 

4.5 

5.9 

8.0 

1900 

8.18 

10.82 

14.79 

4.3 

5.7 

7.8 

2000 

8.30 

11.07 

15.20 

4.1 

5.5 

7.6 

2100 

8.47 

11.40 

15.81 

4.0 

5.4 

7.5 

2200 

8.61 

11.66 

16.24 

3.9 

5.3 

7.4 

2300 

8.82 

12.02 

16.81 

3.8 

5.2 

7.3 

2400 

9.00 

12.32 

17.28 

3.7 

5.1 

7.2 

2500 

9.19 

12.61 

17.75 

3.7 

5.0 

7.1 

2600 

9.38 

12.93 

18.22 

3.6 

5.0 

7.0 

2700 

9.56 

13.21 

18.64 

3.5 

4.9 

6.9 

2800 

9.73 

13.44 

18.97 

3.5 

4.8 

6.8 

2900 

9.90 

13.68 

19.31 

3.4 

4.7 

6.7 

3000 

9.98 

13.95 

19.69 

3.3 

4.6 

6.6 

depend  somewhat  on  the  distance  hauled.  Table  6  shows  this  effect 
for  distances  of  100,  500,  and  900  feet  respectively,  which  are  the 
approximate  minimum,  average,  and  maximum  distances  hauled  on 
the  area  studied.  The  following  sample  computation  will  illustrate 
the  method  of  derivation  of  the  table. 


14  UNIVERSITY    OF    CALIFORNIA — EXPERIMENT    STATION 


For  a  100-foot  Log  Hauled  a  Distance  of  100  Feet 

"Out"  outside  of  bull  block. 24  minutes  (table  3,  column  2) 

"Out  delay"  outside  bull  block  30  minutes  (table  3,  column  3) 

"In"  outside  of  bull  block  34  minutes  (table  3,  column  4 

and  table  5,  column   2 — 
.39  X  .865) 

"In  delay"  outside  of  bull  block 13  minutes  (table  3,  column  5 

and  table  5,  column  3 — 
.34  X  .38) 

"Hook" 50  minutes  (table  5,  column  4) 

"In"  inside  of  bull  block 42  minutes  (table  5,  column  5) 

"In  delay"  inside  of  bull  block 19  minutes  (table  5,  column  6) 

All  other  items  except  general  delays 3.94  minutes   (page  8) 

Total 6.06  minutes 

"General  delays"  (15.8  per  cent) 96  minutes 

Grand  total 7.02  minutes 

The  second,  third,  and  fourth  columns  of  the  table  give  the  values 
thus  computed.  The  last  three  columns  give  the  same  values  divided 
by  the  average  volume  of  the  class,  or,  in  other  words,  the  time  per 
m.b.m.  It  will  be  observed:  (1)  the  importance  of  distance  is  rela- 
tively greater  in  the  case  of  large  logs  than  in  that  of  small;  (2)  the 
importance  of  log  size  is  relatively  greater  for  short  distances  than 
for  long;  (3)  for  all  distances  the  very  small  logs  are  exorbitantly 
expensive  to  handle. 

Influence  on  Time  of  Variations  in  Size  of  Trees  from  which 

Logs  are  Made 

It  now  remains  to  correlate  these  facts  with  tree  diameter  instead 
of  log  diameter.  To  determine  this  relation  requires  a  knowledge 
not  only  of  the  average  gross  volume  of  trees  of  various  diameters, 
but  also  of  how  each  size  was  subdivided  into  logs  for  yarding.  Both 
of  these  facts  were  given  in  the  previous  study  already  referred  to,3 
and  they  are  therefore  merely  recapitulated  in  the  second  column 
of  table  7.  A  single  figure  opposite  a  diameter  class  indicates  that 
trees  of  this  size  were  yarded  as  a  single  log;  two  figures  indicate 
that  two  logs  were  made  thereof,  and  so  on. 

The  third  column  of  this  table  is  taken  from  column  3  of  table  6 
(interpolated).  In  this,  however,  "spot"  and  "spot  delays"  are 
treated  as  constants,  which  is  hardly  justifiable  in  computations 
based  on  the  tree  as  the  unit.  The  only  feasible  method  of  readjust- 
ing this  item  of  time  seems  to  be  to  assume  that  the  "spot"  and 
"spot  delay"  times  should  be  distributed  in  the  same  proportions  as 
the  time  spent  by  the  steam  saw  in  sawing  trees  of  the  same  sizes. 

»  Bulletin  339  of  this  series,  page  330,  table  14. 


Bulletin  371]        THE  rela.tive  COST  OF  YARDING  TIMBER 


15 


TABLE  7 

Influence  of  Variations  in  Tree  Diameter  on  Time  of  Yarding  a  Distance 

of  500  Feet 

STUDY  A 


"Spot" 

and 

Total 

"spot 

time  all 

Tree 

Same, 

delay" 

items 

diam- 

Gross 

less  1.46 

corrected 

including 

eter 

scale 

Time- 

for  "spot" 

Time 

to  be 

revised 

Total 

breast 

of  logs — 

cost  all 

and  "spot 

for  steam 

propor- 

"spot" 

time  per 

Same, 

high, 

Scribner, 

items, 

delay," 

sawing, 

tional 

and  "spot 

M.B.M., 

curved, 

inches 

M.B.M. 

minutes 

minutes 

minutes 

to  steam 
sawing, 
minutes 

delay," 
minutes 

minutes 

minutes 

18 

.161 

8.48 

7.02 

5.0 

.53 

7.55 

46.8 

46.8 

20 

.279 

8.57 

7.11 

5.1 

.54 

7.65 

27.4 

27.5 

22 

.464 

8.71 

7.25 

8.0 

.85 

8.10 

17.4 

18.2 

24 

.526 

8.76 

7.30 

8.3 

.88 

8.18 

15.6 

14.7 

26 

.647 

8.86 

7.40 

8.8 

.94 

8.34 

12.9 

11.8 

28 

1.009 

9.21 

7.75 

12.7 

1.35 

9.10 

9.0 

10.0 

30 

1.150 

9.37 

7.91, 

13.7 

1.46 

9.37 

8.2 

9.0 

32 

1.351 
.503 

9.76 

8.73 

8.30 

14.7 

1.57 

9.87 

7.3 

8.4 

34 

1.425 

9.78 

15.59 

16.5 

1.76 

17.35 

9.0 

1.928 

18.51 

8.0 

.559 

8.78 

36 

1.616 

10.16 

16.02 

17.8 

1.90 

17.92 

8.2 

2.175 

18.94 

7.5 

.640 

8.85 

38 

1.792 

10.55 

16.48 

19.3 

2.05 

18.53 

7.6 

2.432 

19.40 

7.2 

.694 

8.88 

40 

1.941 

10.93 

16.89 

20.8 

2.22 

19.11 

7.3 

2.635 

19.81 

6.8 

.789 

8.98 

42 

2.119 

11.43 

17.49 

22.7 

2.42 

19.91 

6.8 

2.908 

20.41 

6.6 

2.094 

11.36 

44 

1.723 

11.41 

19.85 

30.0 

3.20 

23.05 

6.0 

3.817 

22.77 

6.3 

.845 

9.03 

1.441 

9.82 

46 

1.991 

11.06 

25.53 

26.4 

2.81 

28.34 

6.6 

4.277 

29.91 

6.1 

.917 

9.10 

1.586 

10.05 

48 

2.149 

11.52 

26.29 

28.9 

3.08 

29.37 

6.3 

4.652 

30.67 

6.0 

16  UNIVERSITY    OF    CALIFORNIA— EXPERIMENT    STATION 

Column  4  gives  the  results  of  deducting  the  constant  "spot"  and 
"spot  delay"  times,  while  column  5  gives  the  steam  saw  times,  based 
on  the  table  just  referred  to  in  Bulletin  339,  which  may  be  used  in 
redistributing  them.  Column  6  gives  the  revised  "spot"  and  "spol 
delay"  times.  At  the  average  load,  1200  feet  b.m.,  which  results 
from  a  30-inch  tree,  the  average  value  of  1.46  minutes  is  adopted. 

1  46 

Since  this  is  — —   or  .1065  times  the  steam  saw  time,  the  remaining 

J.  O.  I 

"spot"  and  "spot  delay"  times  are  calculated  by  multiplying  the 
steam  saw  time  of  each  size  class  by  this  figure.  Column  7  is  the  sum 
of  columns  5  and  6 ;  column  8  is  column  7  divided  by  column  2,  with 
the  decimal  shifted  to  express  results  in  m.b.m.  The  final  column 
is  a  graphical  readjustment  of  column  8. 

This  final  column  indicates  that  for  the  average  yarding  distance 
it  costs  7.8  times  as  much  to  yard  18-inch  trees  as  48-inch  trees,  a 
ratio  which  is  unaffected  by  the  translation  of  the  figures  into  dollars 
and  cents  as  was  clone  in  table  1. 


STUDY  B 

This  study  was  located  on  an  area  similar  to  that  of  Study  A. 
As  illustrated  by  the  map  of  figure  3,  the  topography  was  gentle  and 
the  yarding  chance  nearly  ideal.  The  timber  also  was  similar  except 
that  the  stand  was  in  this  instance  about  24  m.b.m.  per  acre,  a  more 
normal  value  for  this  region.  The  study  covered  a  complete  setting, 
or  about  66  acres,  the  yarder  changing  its  position  to  face  in  the 
opposite  direction  when  about  half  of  the  area  had  been  yarded.  The 
yarder  used  was  (like  that  in  Study  A)  a  10  by  11  simple-geared 
wide-drum  machine  made  by  the  Willamette  Iron  and  Steel  Works. 
The  logs  were  handled  in  long  lengths  but  were  dropped  by  this 
engine  at  the  bull  block,  where  they  were  picked  up  by  a  swing 
donkey  which  hauled  them  the  remaining  300  feet  to  the  landing  and 
spotted  them  for  the  steam  saw.  The  swing  engine  was  a  9%  by  11 
"Cracker jack"  yarder  made  by  the  same  company.  This  method  of 
handling  increased  not  only  the  equipment  and  crew  but  also  the 
daily  output  as  well,  since  the  yarding  engine  was  relieved  of  a 
considerable  amount  of  work  which  would  otherwise  have  been 
required  of  it.  The  use  of  two  engines  necessitated  separate  studies 
of  their  operations.  The  data  collected  were,  however,  essentially  the 
same  as  before. 


Bulletin  371]         THE  RELATIVE  COST  OF  YARDING  TIMBER 


17 


Fig.  3. — Contour  map  of  yarding  area  of  Study  B,  showing  (A)  railroad, 
(B)  landing,  (C)  bucking  chutes,  (D)  positions  of  yarder,  (E)  positions  of 
swing,  and  the  positions  of  the  yarding  line. 


As  in  Study  A,  most  of  the  log's  were  handled  singly.  A  few  logs 
were,  on  account  of  their  convenient  position,  hauled  by  the  swirig 
donkey  only.  The  operation  required  for  its  completion  19  working 
days  for  the  yarder  and  20  for  the  swing.  The  average  load  per 
trip  was  1403  feet  b.m.    The  crew  emphn^ed  was  as  follows : 


18 


UNIVERSITY    OF    CALIFORNIA EXPERIMENT    STATION 


Yarder 

1  hooktender      3%  riggers4 

1  engineer  1  chaser 

1  fireman  1  frogger 

1  wood  buck 

1  choker  hole  digger 

1  whistle  punk 


Swing 
1  hooktender 


y2 


engineer 
fireman 


%  wood  buckE 


chute  tender 
whistle  punke 


As  in  Study  A  the  fuel  burned  was  mill  slabs,  the  value  thereof 
not  being  included  in  the  costs,  and  a  horse  was  used  in  changing  line. 
The  subdivision  of  the  average  trip  of  yarder  and  swing  into  its  time 
elements  is  given  in  tables  8  and  9  respectively,  which  correspond  to 
table  2  of  Study  A. 

TABLE  8 
Distribution  of  Time  between  Operations  Involved  in  Yarding 

STUDY  B 


Operation 


Average  time 
of  trip — 
minutes 


Per  cent  of 
total 
time 


Average  time 

per 

occurrence — 

minutes 


Out 

Shift 

Taking  off  choker 

Hook ..... 

Total  time  between  out  and  in. 
In 


.94 


Block7 

Unhook 

Delays — Out 

Choker  dropped 

Miscellaneous 

Delays — In 

Hung  up  on  stumps,  trees,  logs  and 
slash 

Avoiding  stumps,  trees,  logs  and  slash 

Waiting  for  limbing 

Insufficient    power    and   waiting  for 
steam 

Miscellaneous 

Delays — General 

Changing  line 

Waiting  for  swing 

Engine  trouble 

Repairing  lines,  blocks,  etc 

Miscellaneous 

Total  delays 


.94 
.29 
.20 
.86 

1.35 

1.17     1.17 

.09       .09 

.55       .55 

.01 
.02 


.97 
.13 
.20 

.27 
.16 

1.22 

.52 
.04 
.37 
.31 


Total  time  per  trip 


4.22 


8.12 


11.4 
3.5 
2.4 

10.3 

14.0 
1.1 

6.6 

.1 

.2 


11.7 
1.6 

2.4 

3.2 
1.9 

14.7 

6.3 

.5 

4.5 

3.6 


11.4 


16.2 

14.0 

1.1 

6.6 


50.7 
100.0 


1 


.95 
.43 

.28 
.86 

06 
.88 
.55 

.85 
.59 


2.21 
1.31 
2.20 

2.39 


15.32 
3.07 
3.62 

10.34 


*  A  fourth  rigger  was  employed  on  6  out  of  19  days. 

5  One-third  of  the  wood  buck 's  time  was  charged  to  the  loader. 

6  The  whistle  punk  was  laid  off  after  the  first  10  days. 

7  Since  logs  were  not  passed  around  the  inner  bull  block  this  item  occurred 
only  in  trips  where  a  second  bull  block  was  used. 


Bulletin  371]       THe  relative  cost  of  yarding  timber 


19 


TABLE  9 
Distribution  of  Time  between  Operations  Involved  in  Swinging 

STUDY  B 


Operation 

Average  time 

per  trip — 

minutes 

Per  cent  of 
total 
time 

Average  time 

per 

occurrence — ■ 

minutes 

Out 

.47       .47 
3.70    3.70 

.67       .67 
1.75     1.75 

.75       .75 

.01 

.31 
.12 
.11 
.05 

.16 
.18 
.10 
.10 
.22 

1.36 

8.70 

5.4      5.4 
42.5     42.5 

7.7      7.7 
20.1     20.1 

8.6       8.6 
.1 

3.6 

1.4 

1.3 

.6 

1.8 
2.1 
1.2 
1.1 
2.5 

15.7 

100.0 

.47 

Hook8 

3.70 

In 

.67 

Spot 

1.75 

Unhook 

.75 

Delays — out — miscellaneous 

.32 

Delays — in 

Chute  trouble 

1.80 

Changing  choker 

.94 

Miscellaneous 

Delays — spot — steam  saw  trouble 

5.46 

Delays — general 

Waiting  for  cars 

23.40 

Waiting  for  yarder 

70.68 

Landing  blocked 

1.58 

Repairing  chute 

114.69 

Miscellaneous 

Total  delays 

Total  time  per  trip 

Influence  on  Time  of  Variations  in  Distance  which  Log  is  Hauled 

As  in  the  previous  study,  these  figures  have  been  analyzed  by  first 
determining  the  effect  on  time  of  distance  and  then,  with  proper 
allowances  for  the  variations  from  the  average  distance  of  the  distance 
which  individual  logs  had  to  be  hauled,  the  effect  on  time  of  the  load. 
Since  the  distance  hauled  by  the  swing  was  constant,  the  influence  of 
varying  distance  required  investigation  in  the  case  of  the  yarder  only. 
Table  10  gives  information  similar  to  that  of  tables  3  and  4  of  Study  A 
combined.  The  first  five  columns  are  parallel  to  the  similar  columns 
of  table  3,  while  computations  like  those  of  table  4  are  indicated  by 
columns  6,  7,  and  8.  The  constant  items  independent  of  distance  in 
the  present  instance  are: 

"Hook"    86  minutes  per  trip 

"Shift".... .29  minutes  per  trip 

"Taking  off  choker" 20  minutes  per  trip 

"Block" 09  minutes  per  trip 

"Unhook" 55  minutes  per  trip 

Total 1.99  minutes  per  trip 

s  This  operation  was  constantly  delayed  by  work  of  yarder. 


20 


UNIVERSITY    OF    CALIFORNIA EXPERIMENT    STATION 


The  general  delays  amount  to  29.6  per  cent  of  the  total  time  and  the 

296 
pro-rating  coefficient  is  therefore  „  „n'n  ' — nn„  =  .420,  the  value  used 


in  computing  the  final  column. 


1.000  — .296 


TABLE  10 

Influence  of  Variations  in  Distance  on  Total  Time  of  Yarding  per  Trip 

STUDY  B 


Time 

per  trip — minutes 

Total 

Distance 

including 

yarded, 

Items 

Total, 

42.0 

feet 

"Out" 

"Out 

"In" 

"In 

independent 

exclusive  of 

per  cent  for 

delay" 

delay" 

of 
distance 

general 
delays 

general 
delays 

50 

.12 

.02 

.13 

.20 

1.99 

2.46 

3.47 

100 

.21 

.02 

.24 

.36 

1.99 

2.82 

4.01 

150 

.31 

.02 

.36 

.53 

1.99 

3.21 

4.55 

200 

.40 

.02 

.47 

.70 

1.99 

3.58 

5.08 

250 

.50 

.02 

.58 

.86 

1.99 

3.95 

5.60 

300 

.59 

.03 

.69 

1.03 

1.99 

4.33 

6.12 

350 

.67 

.03 

.80 

1.18 

1.99 

4.67 

6.61 

400 

.76 

.03 

.91 

1.35 

1.99 

5.04 

7.14 

450 

.85 

.03 

1.01 

1.50 

1.99 

5.38 

7.62 

500 

.93 

.03 

1.12 

1.66 

1.99 

5.73 

8.11 

550 

1.00 

.03 

1.23 

1.82 

1.99 

6.07 

8.61 

600 

1.07 

.03 

.  1.33 

1.96 

1.99 

6.38 

9.06 

650 

1.16 

.03 

1.43 

2.11 

1.99 

6.72 

9.54 

700 

1.24 

.03 

1.53 

2.27 

1.99 

7.06 

10.02 

750 

1.31 

.03 

1.63 

2.41 

1.99 

7.37 

10.46 

800 

1.37 

.03 

1.72 

2.55 

1.99 

7.68 

10.92 

850 

1.44 

.03 

1.83 

2.70 

1.99 

7.99 

11.36 

900 

1.50 

.03 

1.92 

2.84 

1.99 

8.28 

11.79 

950 

1.55 

.03 

2.01 

2.97 

1.99 

8.59 

12.21 

1000 

1.60 

.03 

2.10 

3.11 

1.99 

8.89 

12.62 

1050 

1.64 

.03 

2.19 

3.25 

1.99 

9.17 

13.02 

1100 

1.68 

.03 

2.28 

3.38 

1.99 

9.44 

13.41 

1150 

1.72 

.03 

2.37 

3.51 

1.99 

9.72 

13.80 

1200 

1.75 

.03 

2.46 

3.63 

1.99 

9.96 

14.18 

Effect  on  Time  of  Variations  in  Size  of  Log 

Table  11  shows  the  influence  of  the  size  of  log  hauled  on  the  items 
that  are  affected  thereby,  that  is,  the  ' Vin, "  "in  delay, ' '  and  ' ' hook. ' ' 
This  corresponds  to  table  5  of  Study  A. 

Table  12  corresponds  to  table  6  and  shows  the  effect  of  log  volume 
hauled  on  the  complete  yarding  time  per  trip  for  different  distances. 
Since  the  maximum  yarding  distance  in  the  second  study  was  slightly 
greater,  columns  for  1100  feet  are  included  in  this  table  in  addition 
to  those  for  100,  500,  and  900  feet.  It  will  be  observed  that  the  con- 
clusions of  the  first  study  (page  14)  are  equally  justified  for  Study  B. 


Bulletin  371]         THE  RELATIVE  COST  OF  YARDING  TIMBER 


21 


TABLE   11 
INFLUENCE  OF  VARIATIONS   IN  SIZE  OF  LOG  ON  YARDING  TIMES   AFFECTED   THEREBY' 

STUDY  B 


Volume  of  log, 

gross  scale, 

Scribner, 

feet,  b.m. 

"In," 

per  cent  of  average 

time  for  corresponding 

distances 

"In  delay," 

per  cent  of  average 

time  for  corresponding 

distances 

"Hook," 
minutes 

100 

93.8 

31 

.79 

200 

93.9 

32 

.79 

300 

94.0 

33 

.79 

400 

94.1 

35 

.79 

500 

94.2 

37 

.80 

600 

94.3 

40 

.80 

700 

94.4 

43 

.80 

800 

94.6 

47 

.80 

900 

95.0 

51 

.81 

1000 

95.4 

55 

.81 

1100 

95.8 

59 

.81 

1200 

96.3 

65 

.81 

1300 

96.8 

71 

.82 

1400 

97.3 

77 

.82 

1500 

97.8 

84 

.83 

1600 

98.7 

91 

.83 

1700 

99.7 

99 

.84 

1800 

100.7 

107 

.84 

1900 

101.7 

116 

.85 

2000 

103.1 

126 

.87 

2100 

104.5 

137 

.88 

2200 

106.1 

152      . 

.90 

2300 

107.7 

169 

.92 

2400 

109.7 

191 

.94 

2500 

111.7 

215 

.97 

2600 

113.7 

245 

1.00 

2700 

116.3 

275 

1.02 

2800 

118.9 

306 

1.05 

2900 

121.7 

338 

1.08 

3000 

124.8 

370 

1.12 

3100 

128.5 

402 

1.16 

3200 

132.3 

435 

1.19 

3300 

136.5 

469 

1.23 

3400 

140.5 

504 

1.27 

3500 

144.8 

539 

1.32 

Table  13  gives  similar  information  for  the  swing.  In  this,  the 
distance  being  fixed,  the  actual  times  for  the  various  items  can  be 
used.  The  "items  independent  of  distance"  (column  5)  are  as  follows : 

"Out" 47  minutes  per  trip 

"Out  delay" 01  minutes  per  trip 

"Spot" 1.75  minutes  per  trip 

"Spot  delay"  05  minutes  per  trip 

-"Unhook" 75  minutes  per  trip 

Total 3.03  minutes  per  trip 


22 


UNIVERSITY    OF    CALIFORNIA — EXPERIMENT    STATION 


TABLE  12 

Influence  of  Variations  in  Size  of  Log  on  Total  Yarding  Time  per  Trip 
for  Different  Distances 

STUDY  B 


Total  time  of  trip,  minutes 

Time  cost  per  M.B.M.  gross, 

minutes 

Volume  of  log,    ' 

Distance  in  feet9 

Distance 

in  feet9 

gross  scale, 

Scribner, 

feet,  b.m. 

100 

500 

900 

1100 

100 

500 

900 

1100 

100 

3.55 

6.30 

8.75 

9.80 

35.46 

63.00 

87.53 

98.04 

200 

3.55 

6.33 

8.80 

9.86 

17.76 

31.65 

44.00 

49.29 

300 

3.56 

6.36 

8.85 

9.91 

11.87 

21.19 

29.82 

33.04 

400 

3.58 

6.41 

8.93 

10.01 

8.94 

16.02 

22.32 

25.03 

500 

3.59 

6.46 

9.01 

10.11 

7.17 

12.90 

18.02 

20.23 

600 

3.61 

6.53 

9.14 

10.26 

6.01 

10.89 

15.24 

17.11 

700 

3.62 

6.61 

9.27 

10.42 

5.18 

9.44 

13.24 

14.88 

800 

3.65 

6.71 

9.43 

10.62 

4.56 

8.38 

11.80 

13.27 

900 

3.68 

6.81 

9.61 

10.83 

4.08 

7.57 

10.48 

12.03 

1000 

3.70 

6.91 

9.79 

11.01 

3.70 

6.92 

9.79 

11.01 

1100 

3.73 

7.02 

9.97 

11.24 

3.39 

6.38 

9.06 

10.22 

1200 

3.76 

7.14 

10.22 

11.55 

3.13 

5.98 

8.53 

9.60 

1300 

3.80 

7.33 

10.49 

11.86 

2.92 

5.64 

8.06 

9.12 

1400 

3.84 

7.48 

10.75 

12.17 

2.74 

5.34 

7.68 

8.68 

1500 

3.89 

7.66 

11.05 

12.53 

2.59 

5.11 

7.36 

8.35 

1600 

3.93 

7.85 

11.37 

12.90 

2.46 

4.91 

7.09 

8.06 

1700 

3.98 

8.06 

11.72 

13.33 

2.34 

4.74 

6.90 

7.85 

1800 

4.04 

8.28 

12.08 

13.75 

2.24 

4.59 

6.70 

7.64 

1900 

4.10 

8.52 

12.49 

14.24 

2.16 

4.48 

6.56 

7.49 

2000 

4.18 

8.80 

12.95 

14.78 

2.09 

4.40 

6.48 

7.39 

2100 

4.26 

9.10 

13.46 

15.38 

2.03 

4.33 

6.41 

7.32 

2200 

4.37 

9.51 

14.13 

16.18 

1.99 

4.32 

6.42 

7.35 

2300 

4.49 

9.96 

14.89 

17.08 

1.95 

4.32 

6.47 

7.42 

2400 

4.65 

10.54 

15.86 

18.28 

1.94 

4.39 

6.61 

7.61 

2500 

4.82 

11.18 

16.93 

19.49 

1.93 

4.47 

6.76 

7.79 

2600 

5.02 

11.96 

18.23 

21.04 

1.93 

4.60 

7.01 

8.09 

2700 

5.21 

12.74 

19.55 

22.63 

1.93 

4.72 

7.25 

8.38 

2800 

5.42 

13.55 

20.91 

24.21 

1.94 

4.84 

7.36 

8.65 

2900 

5.64 

14.40 

22.32 

25.89 

1.94 

4.96 

7.70 

8.93 

3000 

5.87 

15.25 

23.75 

27.58 

1.95 

5.08 

7.92 

9.19 

Influence  on  Time  of  Variations  in  Size  of  Trees  from  which 

Loos  are  Made 

Table  14  shows  the  influence  of  tree  diameter  breast  high  on  costs. 
It  has  been  prepared  in  exactly  the  same  manner  as  table  7  except  for 
the  minor  and  obvious  changes  necessitated  by  the  use  of  two  donkeys 
and  their  crews  in  the  present  instance.  The  times  for  the  yarder 
and  the  swing  cannot  be  combined,  since  their  crews  are  of  different 
size,  and  it  is  only  after  translating  into  dollars  and  cents  that  a  total 
can  be  obtained.  This  translation  and  the  resulting  total  eost  has 
already  been  indicated  in  table  1.     The  final  columns  of  table  14, 


»  This  distance  does  not  include  the  300  feet  hauled  by  the  swing. 


BULLETIN  371]         THE  RELATIVE  COST  OF  YARDING   TIMBER 


23 


however,  again  show  that  a  thousand  feet,  b.m.,  of  logs  from  18-inch 
trees  is  from  six  to  eight  times  as  expensive  to  handle  as  from  48-inch 
trees. 

TABLE  13 
Influence  of  Variations  in  Size  of  Log  on  Time  of  Swing  per  Trip 

STUDY  B 


Volume  of 

log, 

gross  scale, 

Scribner, 

feet,  b.m. 

Time  per  trip  in  minutes 

"Hook" 

"In" 

"In  delay" 

Items 

independent 

of 

of  volume 

Total, 
exclusive 

of 
"general 
delays" 

Total 

including 

9.6  per  cent 

for  "general 

delays" 

100 

1.55 

.65 

.27 

3.03 

5.05 

6.03 

200 

1.65 

.65 

.29 

3.03 

5.62 

6.16 

300 

1.76 

.65 

.31 

3.03 

5.75 

6.31 

400 

1.88 

.65 

.33 

3.03 

5.89 

6.46 

500 

2.01 

.65 

.35 

3.03 

6.04 

6.62 

600 

2.15 

.65 

.37 

3.03 

6.20 

6.80 

700 

2.30 

.65 

.39 

3.03 

6.37 

6.98 

800 

2.45 

.65 

.41 

3.03 

6.54 

7.17 

900 

2.61 

.66 

.43 

3.03 

6.73 

7.37 

1000 

2.76 

.66 

.45 

3.03 

6.90 

7.55 

1100 

2.93 

.66 

.46 

3.03 

7.08 

7.76 

1200 

3.11 

.66 

.48 

3.03 

7.28 

7.98 

1300 

3.30 

.66 

.50 

3.03 

7.49 

8.21 

1400 

3.50 

.66 

.52 

3.03 

7.71 

8.45 

1500 

3.70 

.67 

.54 

3.03 

7.94 

8.69 

1600 

3.91 

.67 

.56 

3.03 

8.17 

8.94 

1700 

4.12 

.67 

.57 

3.03 

8.39 

9.20 

1800 

4.34 

.68 

.59 

3.03 

8.64 

9.47 

1900 

4.58 

.68 

.61 

3.03 

8.90 

9.75 

2000 

4.81 

.69 

.63 

3.03 

9.14 

10.03 

2100 

5.06 

.69 

.65 

3.03 

9.43 

10.33 

2200 

5.36 

.70 

.68 

3.03 

9.77 

10.70 

2300 

5.70 

.70 

.70 

3.03 

10.13 

11.10 

2400 

6.07 

.71 

.73 

3.03 

10.54 

11.55 

2500 

6.49 

.71 

.77 

3.03 

11.00 

12.05 

2600 

6.93 

.72 

.81 

3.03 

11.49 

12.59 

2700 

7.43 

.73 

.86 

3.03 

12.05 

13.21 

2800 

7.95 

.74 

.94 

3.03 

12.66 

13.87 

2900 

8.51 

.74 

1.02 

3.03 

13.30 

14.57 

3000 

9.11 

.75 

1.11 

3.03 

14.00 

15.35 

STUDY  C 

This  study  was  made  under  conditions  which  differed  radically 
from  those  already  described.  The  yarding  area,  as  will  be  seen  from 
the  map  of  figure  4,  was  fairly  typical  of  the  west  side  of  the  central 
Sierra  and  is  characterized  by  broken  topography  and  steep  slopes  up 
which  the  timber  was  hauled  to  the  railroad  located  near  the  ridge 
top.  The  timber  was  a  mixed  stand  of  sugar  pine,  western  yellow 
pine  (California  white  pine),  Douglas  fir,  white  fir,  and  incense  cedar, 


24 


UNIVERSITY    OF    CALIFORNIA EXPERIMENT    STATION 


averaging  about  39  m.b.m.  per  acre  for  the  area  actually  yarded. 
The  maximum  size  of  the  logs  was  nearly  twice  as  large  as  it  was  in 
Studies  A  and  B,  and  the  trees  were  much  taller. 


TABLE  14 

Influence  of  Variations  in  Tree  Diameter  on  Time  of  Yarding  a  Distance 

of  500  .Feet  and  Swinging 

STUDY  B 


Swing 

Total  time 
per  M.B.M., 

Same 

"Spot" 

and 

"spot 

delay" 

3urved, 

Yard- 

Same 
less 

Total 
includ- 

Tree 
diam- 
eter 

breast 

high, 

inches 

Gross 

scale 

of  logs, 

Scrib- 

ner, 
M.B.M. 

ing; 

time 

all 

items, 

(Table 

12), 
minutes 

Time 

all 
items, 
(Table 

13), 
minutes 

1.8 

for 
"spot" 

and 

"spot 

delay," 

minutes 

Time 
for 

steam 

sawing, 

minutes 

cor- 
rected 
to  be 
propor- 
tional 

to 
steam 
sawing, 
minutes 

ing 
revised 
"spot" 

and 

"spot 

delay," 

minutes 

Yarder 
minutes 

Swing 
minutes 

Yarder 
minutes 

Swing 
mimites 

18 
20 
22 
24 
26 
28 
30 
32 

.161 

.279 

.464 

.526 

.647 

1.009 

1.150 

1.351 

6.3 
6.3 
6.4 
6.5 
6.6 
6.9 
7.1 
7.4 

6.1 
6.3 
6.6 
6.7 
6.9 
7.6 
7.9 
8.3 

4.3 
4.5 
4.8 
4.9 
5.1 
5.8 
6.1 
6.5 

5.0 

5.1 

8.0 

8.3 

8.8 

12.7 

13.7 

14.7 

.6 
.6 
1.0 
1.0 
1.1 
1.6 
1.7 
1.8 

4.9 
5.1 
5.8 
5.9 
6.2 
7.4 
7.8 
8.3 

39.2 

22.6 

13.8 

12.4 

10.2 

6.8 

6.2 

5.5 

30.4 

18.3 

12.5 

11.2 

9.6 

7.3 

6.8 

6.1 

39.2 

22.5 

15.5 

11.5 

9.2 

7.8 

6.9 

6.3 

30.4 

18.5 

13.5 

10.7 

9.0 

8.0 

7.3 

6.7 

34 

.503 
1.425 

6.5 

7.5 

14.0 

6.6 
7.1 

13.7 

4.8 
5.3 

10.1 

16.5 

2.0 

12.1 

7.3 

6.3 

5.9 

1.928 

6.4 

36 

.559 
1.616 

6.5 
7.9 

6.7 
9.0 

4.9 

7.2 

2.175 

14.4 

15.7 

12.1 

17.8 

2.2 

14.3 

6.6 

6.6 

5.7 

6.1 

38 

.640 
1.792 

6.6 
8.3 

6.9 
9.5 

5.1 

7.7 

2.432 

14.9 

16.4 

12.8 

19.3 

2.4 

15.2 

6.1 

6.2 

5.5 

5.8 

40 

.694 
1.941 

6.6 
8.6 

7.0 
9.9 

5.2 

8.1 

2.635 

15.2 

16.9 

13.3 

20.8 

2.5 

15.8 

5.8 

6.0 

5.4 

5.6 

42 

.789 
2.119 

6.7 
9.2 

7.1 
10.4 

5.3 

8.6 

2.908 

15.9 

17.5 

13.9 

22.7 

2.8 

16.7 

5.5 

5.7 

5.3 

5.5 

44 

2.094 
1.723 

9.1 
8.1 

10.3 
9.3 

8.5 
7.5 

3.817 

17.2 

19.6 

16.0 

30.0 

3.7 

19.7 

4.5 

5.2 

5.2 

5.3 

46 

.845 
1.441 
1.991 

6.8 
7.5 
8.8 

7.3 

8.6 

10.0 

5.5 
6.8 
8.2 

4.277 

23.1 

25.9 

20.5 

26.4 

3.2 

23.7 

5.4 

5.6 

5.1 

5.2 

48 

.917 
1 .  586 
2.149 

6.8 
7.8 
9.3 

7.4 

8.9 

10.5 

5.6 
7.1 
8.7 

4.652 

23.9 

26.8 

21.4 

28.9 

3.7 

25.1 

5.1 

5.4 

5.0 

5.1 

BULLETIN  371]         THE  RELATIVE  COST  OF  YARDING  TIMBER  25 


Fig.  4. — Contour  map  of  yarding  area  of  Study  C,  showing  (A)  railroad, 
(B)  landing,  (C)  bucking  chutes,  CD)  positions  of  yarder,  (E)  positions  of 
swing,  and  the  positions  of  the  yarding  line.     Scale,  1  inch  equals  450  feet. 


26  UNIVERSITY    OF    CALIFORNIA EXPERIMENT    STATION 

The  study  covered  a  full  setting  of  the  yarder,  or  about  43  acres, 
the  engine  shifting  its  position  to  the  opposite  end  of  the  landing 
when  about  half  of  the  timber  had  been  removed.  An  additional 
minor  shift  in  position  was  made  (as  indicated  on  the  map)  to  avoid 
the  necessity  of  using  a  bull  block  on  certain  of  the  turns.  The 
yarding  engine  was  a  12  by  14  "Humboldt  Yarder"  manufactured 
by  the  Willamette  Iron  and  Steel  Works.  This  narrow-drum  type  of 
machine  permitted  the  use  of  a  "fair  lead"  which  made  it  possible 
to  dispense  with  a  bull  block  on  a  large  number  of  trips.  A  swing 
donkey,  a  12  by  14  simple-geared,  wide-drum  Willamette  reader,  was 
used  in  a  manner  similar  to  that  of  Study  B,  its  hauling  distance 
being  about  350  feet.  The  haul  of  the  swing  was,  however,  parallel 
to  the  track  so  that  the  hauling  distance  of  the  yarder  was  not 
materially  reduced  thereby.  Its  function  was,  therefore,  merely  to 
relieve  the  yarder  of  the  duty  of  spotting  for  the  steam  saw.  Logs 
were  normally  handled  one  at  a  time. 

The  average  load  per  trip  was  1283  feet  b.m.  gross  scale.  The 
operation  required  15%  days  for  both  yarder  and  swing.  The  location 
of  the  railroad,  landing,  bucking  chute;  yarder,  swing,  etc.,  are  shown 
on  the  map. 

The  crew  employed  was  as  follows : 

Yarder  Swing 

1  hooktender  1  engineer 

1  engineer  1  fireman 

1  fireman  1  wood  haul  teamster 

1  wood  haul  teamster  1  wood  haul  team 

1  wood  haul  team  1  unhooker 

3  riggers  1  frogger 

1  frogger  1%  frog  shoveler10 
1  choker  hole  digger 
1  whistle  punk 

The  data  obtained,  similar  in  general  to  that  of  the  studies  pre- 
viously described,  is  summarized  in  table  15,  which,  however,  gives 
somewhat  less  detail  as  to  the  causes  of  the  delays.  Table  16  is  a 
summary  for  the  swing. 


io  Two  frog  shovelers  were  used  on  15  out  of  25  days  and  one  on  the  remainder. 


BULLETIN  371]         THE  RELATIVE  COST  OF  YARDING  TIMBER 


27 


TABLE  15 

Distribution  of  Time  between  Operations  Involved  in  Yarding 
STUDY  C 


Operation 

Average  time 

per  trip — 

minutes 

Per  cent  of 
total 
time 

Average  time 

per 

occurrence — 

minutes 

Out 

1.16     1.16 
.20 
.76 

.96 

2.58 
.12 

2.70 
.22       .22 
.97       .97 

.52 
.09 
.06 
1.58 
.15 
.03 
.24 

1.03 
.90 

4.60 

10.61 

10.9     10.9 
1.9 
7.2 

9.1 
24.3 
1.1 

25.4 
2.1       2.1 
9.1       9.1 

4.9 

.9 

.6 

14.9 

1.4 

.3 
2.3 

9.7 
8.4 

43.4 

100.0 

1.16 

Shift 

.20 

Hook 

.76 

Total  time  between  out  and  in 

In  outside  of  block 

2.58 

In  inside  of  block 

.39 

Total  in 

Block 

.75 

Unhook 

.97 

Delays — 

Out 

Shift 

Hook 

In  outside  of  block 

In  inside  of  block 

Block 

Unhook 

General — 

Line  changes 

21.95 

Miscellaneous 

Total  delays 

Total  time  per  trip 

TABLE  16 

Distribution  of  Time  between  Operations  Involved  in  Swinging 
STUDY  C 


Operation 

Average  time 

per  trip — 

minutes 

Per  cent  of 
total 
time 

Average  time 

per 

occurrence — 

minutes 

Out ; 

.41       .41 
4.44     4.44 

.96       .96 
1.97     1.97 
1.10     1.10 

.13 

1.11 

.17 

.03 

.76 

2.20 

11.08 

3.7      3.7 
40.0    40.0 

8.6       8.6 
17.8     17.8 
10.0     10.0 

1.1 

10.2 

1.5 

.2 

6.9 

19.9 

100.0 

.41 

Hook 

4.94 

In 

.96 

Spot 

2.09 

Unhook 

1.17 

Delays — 

Out 

In 

Spot 

Unhook 

General 

Total  delays 

Total  time  per  trip 

23 


UNIVERSITY    OF    CALIFORNIA EXPERIMENT    STATION 


Influence  on  Time  of  Variations  in  Distance  which  Log  is  Hauled 

The  analysis  of  the  yarder  figures  to  determine  the  influence  of 
variations  of  distance  is  summarized  in  table  17,  which  may  be  com- 
pared to  tables  3,  4,  and.  10.  In  the  present  instance  it  will  be  noted 
that  "hook"  appears  as  one  of  the  variables,  although  previously 
treated  as  a  constant.  The  variation  in  the  values  of  this  item  which 
necessitated  this  treatment  may  be  the  result  of  the  longer  yarding 


TABLE  17 
Influence  of  Variations  in  Distance  on  Total  Time  of  Yarding  per  Trip 

STUDY  C 


Time  per  trip,  minutes 

Dis- 
tance, 
feet 

"Out" 

"Out 
delay" 

"In" 

"In 

delay" 

"Hook" 

Items 
indepen- 
dent of 
distance 

Total, 
exclusive 
of  general 

delays 

Total 
including 
22.1  per 
cent  for 
general 
delays 

50 

.37 

.40 

.22 

.14 

.69 

2.08 

3.90 

4.76 

100 

.40 

.40 

.37 

.22 

.69 

2.08 

4.16 

5.08 

150 

.44 

.41 

.52 

.29 

.69 

2.08 

4.43 

5.41 

200 

.48 

.42 

.67 

.37 

.69 

2.08 

4.71 

5.75 

250 

.53 

.42 

.82 

.45 

.69 

2.08 

4.99 

6.10 

300 

.57 

.43 

.97 

.54 

.69 

2.08 

5.28 

6.45 

350 

.62 

.43 

1.13 

.63 

.69 

2.08 

5.58 

6.81 

400 

.67 

.44 

1.29 

.72 

.69 

2.08 

5.89 

7.19 

450 

.72 

.45 

1.45 

.80 

.69 

2.08 

6.19 

7.55 

500 

.78 

.46 

1.62 

.88 

.69 

2.08 

6.51 

7.95 

550 

.84 

.47 

1.78 

.97 

.69 

2.08 

6.83 

8.34 

600 

.91 

.48 

1.95 

1.06 

.69 

2.08 

7.17 

8.75 

650 

.97  • 

.49 

2.12 

1.15 

.69 

2.08 

7.50 

9.16 

700 

1.02 

.50 

2.29 

1.25 

.69 

2.08 

7.83 

9.56 

750 

1.08 

.51 

2.47 

1.35 

.69 

2.08 

8.18 

9.99 

800 

1.15 

.52 

2.64 

1.44 

.69 

2.08 

8.52 

10.40 

850 

1.22 

.53 

2.82 

1.54 

.69 

2.08 

8.88 

10.84 

900 

1.28 

.54 

3.00 

1.64 

.69 

2.08 

9.23 

11.27 

950 

1.35 

.55 

3.18 

1.73 

.70 

2.08 

9.59 

11.70 

1000 

1.43 

.56 

3.37 

1.83 

.71 

2.08 

9.98 

12.19 

1050 

1.51 

.57 

3.56 

1.93 

.72 

2.08 

10.37 

12.65 

1100 

1.59 

.58 

3.75 

2.04 

.73 

2.08 

10.77 

13.15 

1150 

1.67 

.59 

3.95 

2.15 

.75 

2.08 

11.19 

13.66 

1200 

1.75 

.60 

4.15 

2.26 

.77 

2.08 

11.61 

14.19 

1250 

1.84 

.62 

4.36 

2.37 

.79 

2.08 

12.06 

14.72 

1300 

1.93 

.63 

4.57 

2.48 

.81 

2.08 

12.50 

15.27 

1350 

2.03 

.65 

4.78 

2.59 

.84 

2.08 

12.97 

15.83 

1400 

2.13 

.67 

5.00 

2.70 

.88 

2.08 

13.46 

16.43 

1450 

2.24 

.68 

5.24 

2.82 

.93 

2.08 

13.99 

17.09 

1500 

2.35 

.70 

5.48 

2.94 

.99 

2.08 

14.54 

17.76 

1550 

2.47 

.72 

5.73 

3.07 

1.06 

2.08 

15.13 

18.50 

1600 

2.59 

.74 

5.98 

3.20 

1.14 

2.08 

15.73 

19.20 

1650 

2.73 

.75 

6.25 

3.33 

1.23 

2.08 

16.37 

19.99 

1700 

2.88 

.77 

6.52 

3.47 

1.34 

2.08 

17.06 

20.82 

1750 

3.03 

.79 

6.80 

3.62 

1.47 

2.08 

17.79 

21.71 

1800 

3.18 

.81 

7.12 

3.76 

1.62 

2.08 

18.57 

22.67 

Bulletin  371]        THE  relative  COST  OF  YARDING  TIMBER  29 

distances  involved  in  Study  C,  for  tbe  time  of  the  "hook"  is  uniform 
for  the  shorter  distances.  It  seems  more  probable,  however,  that  this 
increase  for  the  greater  distances  is  accidental  and  due  to  the  very 
rough  topography  at  points  most  remote  from  the  landing  (fig.  4). 
The  constant  "items  independent  of  distance"  (column  7)  are  in  this 

case: 

1 '  Shift ' '  20  minutes 

1  'Block"    22  minutes 

"In"  inside  of  block 12  minutes 

"Unhook" 97  minutes 

"Shift  delay"  09  minutes 

"Hook  delay"  06  minutes 

"Block  delay"   03  minutes 

"In  delay"  inside  of  block  15  minutes 

"Unhook"  delay" 24  minutes 

Total 2.08  minutes 

Since  the  general  delays  amount  to  18.1  per  cent  of  the  total  time 
(table  15).  the  pro-rating  coefficient  for  use  in  the  final  column  is 
.181 


1.000  —  .181 


=  .221. 


Influence  on  Time  of  Variations  in  Size  of  Log 

Table  18  shows  the  influence  of  the  size  of  log  hauled  on  the  items 
which  are  directly  affected  thereby,  that  is  the  "in,"  "in  delay,"  and 
"hook."  This  table. corresponds  to  tables  5  and  11.  The  larger  size 
of  the  timber  handled  in  Study  C  permits  the  statement  in  table  18 
of  values  up  to  nearly  6000  feet,  or  almost  double  the  maximum  size 
of  the  previous  studies. 

Table  19  corresponds  to  tables  7  and  12  and  shows  the  effect  of 
variations  in  the  volume  of  the  log  hauled  on  the  complete  yarding 
time  per  trip  for  different  distances.  On  account  of  the  greater 
yarding  distances  involved  in  the  present  study,  columns  are  in  this 
instance  given  for  trip  distances  of  100,  900,  and  1800  feet,  or  the 
approximate  minimum,  average,  and  maximum  for  the  study.  It  will 
be  observed  that,  for  a  third  time,  the  conclusions  stated  on  page  14 
are  confirmed. 

Table  20  gives  similar  information  for  the  swing  and  may  be  com- 
pared with  table  13.  The  "items  independent  of  volume"  (column  5), 
are  as  follows : 

"Out" 41  minutes  per  trip 

"Out  delay" 13  minutes  per  trip 

"Spot" 1.97  minutes  per  trip 

"Spot  delay" „     .17  minutes  per  trip 

"Unhook"   1.10  minutes  per  trip 

"Unhook"  delays 03  minutes  per  trip 

Total 3.81  minutes  per  trip 


30 


UNIVERSITY    OF    CALIFORNIA-  EXPERIMENT    STATION 


The  pro-rating  coefficient  of  7.4  per  cent  (final  column)  is  based  on  the 
fact  that  the  general  delays  amount  to  6.9  per  cent  of  the  total  time : 

.069 


k 


000  —  .069 


.074 


) 


TABLE  18 

Influence  of  Variations  in  Size  of  Log  on  Yarding  Times  Affected  Thereby 

STUDY  C 


"In," 

"In  delay", 

Volume  of  log, 

per  cent  of 

per  cent  of 

gross  scale, 

average  time  for 

average  time  for 

"Hook," 

Scribner, 

corresponding 

corresponding 

minutes 

feet,  b.m. 

distances 

distances 

100 

97.5 

39 

.64 

200 

97.7 

41 

.66 

300 

98.0 

43 

.68 

400 

98.2 

45 

.69 

500 

98.4 

48 

.70 

600 

98.7 

51 

.71 

700 

98.9 

55 

.73 

800 

99.1 

59 

.74 

900 

99.3 

64 

.75 

1000 

99.5 

68 

.75 

1100 

99.7 

73 

.76 

1200 

99.8 

78 

.77 

1300 

99.9 

84 

.78 

1400 

100.1 

91 

.78 

1500 

100.2 

99 

.79 

1600 

100.3 

108 

.79 

1700 

100.5 

118 

.80 

1800 

100.6 

130 

.80 

1900 

100.7 

142 

.81 

2000 

100.9 

156 

.81 

2100 

101.0 

172 

.81 

2200 

101.1 

185 

.82 

2300 

101.3 

199 

.82 

2400 

101.4 

211 

.82 

2500 

101.5 

224 

.82 

2600 

101.6 

236 

.82 

2700 

101.7 

245 

.83 

2800 

101.9 

255 

.83 

2900 

102.0 

265 

.83 

3000 

102.0 

273 

.83 

3100 

102.1 

280 

.83 

3200 

102.1 

287 

.83 

3300 

102.2 

294 

.83 

3400 

102.2 

299 

.83 

3500 

102.3 

304 

.83 

3600 

102.3 

308 

.83 

3700 

102.4 

312 

.83 

3800 

102.4 

315 

.83 

3900 

102.5 

317 

.83 

4000 

102.5 

319 

.83 

4100 

102.6 

320 

.83 

4200 

102.6 

320 

.83 

4300 

102.6 

321 

.83 

4400 

102.7 

321 

.83 

4500 

102.7 

321 

.83 

4600 

102.7 

321 

.83 

4700 

102.7 

322 

.83 

4800 

102.7 

322 

.83 

4900 

102.7 

322 

.83 

5000 

102.7 

322 

.83 

5100 

102.7 

322 

.83 

5200 

102.7 

322 

.83 

5300 

102.8 

322 

.83 

5400 

102.8 

322 

.83 

5500 

102.8 

322 

.83 

5600 

102.8 

322 

.83 

5700 

102.8 

322 

.83 

5800 

102.8 

322 

.83 

5900 

102.8 

322 

.83 

Bulletin  371]         THE  RELATIVE  COST  OF  YARDING  TIMBER 


31 


TABLE  19 

Influence  of  Variations  in  Size  of  Log  on  Total  Yarding  Time  per  Trip 
for  Different  Distances 

STUDY  C 


Volume 

Total  time  of  trip,  minutes 

Time  cost  per  M.B.M.  gross,  minutes 

of  log, 

Distance  in  feet11 

Distance  in  feet11 

gross  scale, 

Soribner, 

feet,  b.m. 

100 

900 

1800 

100 

900 

1800 

100 

5.97 

9.81 

15.76 

59.70 

98.10 

157.60 

200 

5.99 

9.87 

15.87 

29.95 

49.35 

79.35 

300 

6.01 

9.94 

16.00 

20.03 

33.13 

53.33 

400 

6.04 

9.99 

16.10 

15.10 

25.00 

40.25 

500 

6.06 

10.06 

16.25 

12.12 

20.12 

32.50 

600 

6.09 

10.17 

16.50 

10.15 

16.95 

27.50 

700 

6.12 

10.26 

16.69 

8.74 

14.66 

23.84 

800 

6.14 

10.36 

16.89 

7.68 

12.95 

21.11 

900 

6.17 

10.45 

17.09 

6.85 

11.61 

18.99 

1000 

6.19 

10.57 

17.33 

6.19 

10.57 

17.33 

1100 

6.21 

10.71 

17.66 

5.65 

9.75 

16.06 

1200 

6.24 

10.82 

17.91 

5.20 

9.02 

14.93 

1300 

6.26 

10.96 

18.19 

4.82 

8.43 

13.98 

1400 

6.29 

11.07 

18.51 

4.49 

7.92 

13.23 

1500 

6.32 

11.23 

18.89 

4.21 

7.49 

12.59 

1600 

6.35 

11.46 

19.31 

3.97 

7.16 

12.06 

1700 

6.39 

11.66 

19.78 

3.76 

6.86 

11.63 

1800 

6.41 

11.91 

20.39 

3.56 

6.62 

11.33 

1900 

6.46 

12.17 

21.00 

3.40 

6.42 

11.06 

2000 

6.51 

12.44 

21.63 

3.25 

6.22 

10.82 

2100 

6.56 

12.77 

22.34 

3.12 

6.08 

10.64 

2200 

6.61 

13.04 

22.98 

3.00 

5.93 

10.44 

2300 

6.64 

13.32 

23.60 

2.89 

5.79 

10.26 

2400 

6.67 

13.62 

24.18 

2.78 

5.68 

10.07 

2500 

6.70 

13.89 

24.87 

2.68 

5.56 

9.96 

2600 

6.74 

14.13 

25.42 

2.59 

5.44 

9.78 

2700 

6.77 

14.37 

25.89 

2.51 

5.32 

9.60 

2800 

6.80 

14.54 

26.32 

2.43 

5.20 

9.39 

2900 

6.83 

14.71 

26.72 

2.36 

5.08 

9.20 

3000 

6.85 

14.88 

27.14 

2.28 

4.97 

9.05 

3100 

6.88 

15.02 

27.46 

2.22 

4.85 

8.87 

3200 

6.89 

15.18 

27.79 

2.15 

4.75 

8.69 

3300 

6.91 

15.31 

28.12 

2.09 

4.64 

8.53 

3400 

6.93 

15.41 

28.35 

2.02 

4.54 

8.34 

3500 

6.96 

15.50 

28.57 

1.99 

4.43 

8.16 

3600 

6.97 

15.59 

28.75 

1.94 

4.33 

7.99 

3700 

6.99 

15.68 

28.94 

1.89 

4.24 

7.82 

3800 

6.99 

15.73 

29.08 

1.84 

4.14 

7.65 

3900 

7.00 

15.77 

29.16 

1.79 

4.05 

7.48 

4000 

7.00 

15.81 

29.27 

1.75 

3.98 

7.33 

4100 

7.00 

15.84 

29.32 

1.71 

3.87 

7.15 

4200 

7.00 

15.84 

29.32 

1.67 

3.77 

6.98 

4300 

7.01 

15.88 

29.43 

1.63 

3.69 

6.85 

4400 

7.01 

15.88 

29.43 

1.59 

3.61 

6.69 

4500 

7.01 

15.88 

29.43 

1.56 

3.53 

6.54 

4600 

7.01 

15.90 

29.47 

1.52 

3.45 

6.41 

4700 

7.01 

15.90 

29.47 

1.49 

3.38 

6.27 

4800 

7.01 

15.91 

29.47 

1.46 

3.31 

6.14 

4900 

7.01 

15.91 

29.47 

1.47 

3.25 

6.02 

5000 

7.01 

15.91 

29.47 

1.40 

3.18 

5.90 

5100 

7.01 

15.91 

29.47 

1.38 

3.12 

5.78 

5200 

7.01 

15.91 

29.47 

1.35 

3.06 

5.67 

5300 

7.01 

15.91 

29.47 

1.32 

3.00 

5.57 

5400 

7.01 

15.91 

29.47 

1.30 

2.95 

5.46 

5500 

7.01 

15.91 

29.47 

1.28 

2.89 

5.36 

5600 

7.01 

15.91 

29.47 

1.25 

2.84 

5.27 

5700 

7.01 

15.91 

29.47 

1.23 

2.79 

5.18 

5800 

7.01 

15.91 

29.47 

1.21 

2.75 

5.09 

ii  This  distance  does  not  include  the  350  feet  hauled  by  the  swing. 


H2 


UNIVERSITY    OF    CALIFORNIA EXPERIMENT    STATION 


TABLE  20 
Influence  of  Variations  in  Size  of  Log  on  Time  of  Swing  per  Trip 

STUDY  C 


Time  per  trip  in  minutes 

Volume 
of  log, 

Total 

gross  scale, 

Items 

Total, 

including 

Scribner, 

"Hook" 

"In" 

"In  delay" 

independent 

exclusive  of 

7.4    per    cent 

feet,  b.m. 

of 
volume 

"general 
delays ' ' 

for  "general 
delays" 

100 

2.93 

.70 

.80 

'    3.81 

8.94 

9.60 

200 

3.02 

.72 

.83 

3.81 

9.08 

9.76 

300 

3.12 

.74 

.85 

3.81 

9.22 

9.91 

400 

3.22 

.75 

.87 

3.81 

9.35 

10.05 

500 

3.33 

.77 

.90 

3.81 

9.51 

10.22 

600 

3.45 

.  .78 

.92 

3.81 

9.66 

10.39 

700 

3.59 

.80 

.94 

3.81 

9.84 

10.58 

800 

3.73 

.81 

.97 

3.81 

10.02 

10.78 

900 

3.85 

.83 

.99 

3.81 

10.18 

10.93 

1000 

3.96 

.84 

1.01 

3.81 

10.32 

11.10 

1100 

4.09 

.86 

1.03 

3.81 

10.49 

11.27 

1200 

4.24 

.87 

1.06 

3.81 

10.68 

11.47 

1300 

4.40 

.88 

1.08 

3.81 

10.87 

11.68 

1400 

4.57 

.89 

1.10 

3.81 

11.07 

11.90 

1500 

4.75 

.90 

1.12 

3.81 

11.28 

12.11 

1G00 

4.92 

.91 

1.15 

3.81 

11.49 

12.34 

1700 

5.10 

.92 

1.17 

3.81 

11.70 

12.58 

1800 

5.27 

.93 

1.19 

3.81 

11.90 

12.79 

1900 

5.50 

.93 

1.22 

3.81 

12.16 

13.06 

2000 

5.65 

.94 

1.24 

3.81 

12.34 

13.27 

2100 

5.82 

.94 

1.27 

3.81 

12.54 

13.49 

2200 

5.98 

.95 

1.32 

3.81 

12.76 

13.70 

2300 

6.12 

.96 

1.39 

3.81 

12.98 

13.95 

2400 

6.25 

.96 

1.47 

3.81 

13.19 

14.17 

2500 

6.39 

.97 

1.56 

3.81 

13.43 

14.43 

2600 

6.50 

.97 

1.67 

3.81 

13.65 

14.66 

2700 

6.62 

.98 

1.79 

3.81 

13.90 

14.93 

2800 

6.73 

.98 

1.95 

3.81 

14.17 

15.21 

2900 

6.82 

.98 

2.12 

3.81 

14.43 

15.51 

3000 

6.89 

.99 

2.28 

3.81 

14.67 

15.75 

3100 

6.95 

.99 

2.45 

3.81 

14.90 

16.10 

3200 

7.00 

.99 

2.62 

3.81 

15.12 

16.25 

3300 

7.00 

.99 

2.79 

3.81 

15.29 

16.42' 

3400 

7.00 

1.00 

2.96 

3.81 

15.47 

16.60 

3500 

7.00 

1.00 

3.13 

3.81 

15.64 

16.80 

3600 

7.00 

1.00 

3.30 

3.81 

15.81 

17.00 

3700 

7.00 

1.00 

3.47 

3.81 

15.98 

17.18 

3800 

7.00 

1.00 

3.64 

3.81 

16.15 

17.35 

3900 

7.00 

1.00 

3.81 

3.81 

16.32 

17.54 

4000 

7.00 

1.00 

3.98 

3.81 

16.49 

17.70 

4100 

7.00 

1.00 

4.15 

3.81 

16.66 

17.90 

4200 

7.00 

1.00 

4.32 

3.81 

16.83 

18.09 

4300 

7.00 

1.00 

4.49 

3.81 

17.00 

18.26 

4400 

7.00 

1.00 

4.66 

3.81 

17.17 

18.44 

4500 

7.00 

1.00 

4.83 

3.  SI 

17.34 

18.63 

4600 

7.00 

1.00 

5.00 

3.81    • 

17.51 

18.82 

4700 

7.00 

1.00 

5.17 

3.81 

17.68 

19.00 

4800 

7.00 

1.00 

5.34 

3.81 

17.85 

19.18 

4900 

7.00 

1.00 

5.51 

3.81 

18.02 

19.37 

5000 

7.00 

1.00 

5.69 

3.81 

18.20 

19.55 

5100 

7.00 

1.00 

5.87 

3.81 

18.38 

19.74 

5200 

7.00 

1.00 

6.04 

3.81 

18.55 

19.92 

5300 

7.00 

1.00 

6.22 

3.81 

18.73 

20.14 

5400 

7.00 

1.00 

6.39 

3.81 

18.90 

20.31 

5500 

7.00 

1.00 

6.57 

3.81 

19.08 

20.49 

5600 

7.00 

1.00 

6.74 

3.81 

19.25 

20.68 

5700 

7.00 

1.00 

6.91 

3.81 

19.42 

20.88 

5800 

7.00 

1.00 

7.08 

3.81 

19.59 

21.05 

5900 

7.00 

1.00 

7.25 

3.81 

19.76 

21.21 

bulletin  371]      the  relative  cost  of  yarding  timber  33 

Influence  on  Time  of  Variations  in  Size  of  Trees  from  which 

Logs  are  Made 

The  ratios  between  the  figures  in  both  tables  19  and  20  for  small 
and  large  logs  are  of  approximately  the  same  order  of  magnitude  as 
in  Studies  A  and  B.  Comparing,  for  example,  the  time  per  trip 
(900  feet)  of  a  200012  feet  b.m.  log  as  compared  with  a  100  foot  log, 
it  is  observed  that  Study  A  indicates  (table  6)  that  the  former  is 
about  1.43  times  as  great.  In  Study  B  (tables  12  and  13)  the  same 
ratios  for  yarder  and  swing  are  1.48  and  1.66  respectively,  and  in 
Study  C  (tables  19  and  20),  1.27  and  1.38.  When  the  figures  are 
expressed  on  a  tree  instead  of  on  a  log  basis,  however,  a  considerable 
difference  is  apparent.  This  is  due  not  so  much  to  differences  in 
topography  and  machinery  as  to  those  inherent  in  the  timber  itself. 
In  Study  C  the  trees  were  much  taller,  and  therefore  those  of  small 
diameter  were  considerably  greater  in  volume  than  in  the  case  of 
either  Study  A  or  B. 

Table  21  gives  in  its  first  two  columns  the  average  volume  per  tree 
typically  encountered  in  the  last  study,  and  the  method  of  subdividing 
it  into  logs.  The  practice  indicated  was  not  rigidly  followed  and  these 
figures  should  be  considered  merely  as  approximate  averages.  The 
remaining  columns  of  the  table  are  derived  in  the  manner  already 
described  in  connection  with  table  7.  The  final  columns  show  that  the 
18-inch  trees  cost  5.4  and  4.3  times  as  much  for  yarder  and  swing 
respectively  as  do  the  48-inch  trees. 

If  18-inch  and  48-inch  trees  in  the  present  study  had  been  identical 
in  height  and  volume  with  those  of  Studies  A  and  B,  the  time  per 
m.b.m.  required  by  the  yarder  to  handle  them  would  have  been  61.2 
and  3.5  minutes,  respectively,  while  that  by  the  swing  would  have 
been  50.5  and  8.4.  The  ratios  under  these  conditions  would  have 
been  8.1  for  the  yarder  and  6.0  for  the  swing,  or  nearly  the  same  as 
in  the  previous  instances.  It  is  evident,  therefore,  that  were  the 
relative  cost  of  small  trees  and  large  expressed  on  the  basis  of  the 
volume  per  tree  rather  than  on  that  of  the  diameter,  the  results  of 
the  three  studies  would  be  in  even  closer  agreement. 


12  This  is  about  the  largest  size  commonly  handled.     The   values  for  still 
larger  logs  are  in  somewhat  less  striking  agreement. 


34 


UNIVERSITY    OF    CALIFORNIA EXPERIMENT    STATION 


TABLE  21 

Influence  of  Variations  in  Tree  Diameter  on  Time  of  Yarding  a  Distance 
of  900  Feet  and  Swinging 

STUDY  C 


Gross 

scale 

of  logs, 

Scrib- 

ner, 

M.B.M. 

Yard- 
ing; 
time 
all 
items, 
(Table 

19), 
minutes 

Swing 

Total  time 
per  M.B.M., 

Same  ( 

Time 

all 
items, 
(Table 

20), 
minutes 

Same 

less 

2.14 

for 
"spot" 

and 

"spot 

delay," 

minutes 

Time 

for 
steam 
sawing, 
minutes 

"Spot" 

and 

"spot 

delay" 

cor- 
rected 
to  be 
propor- 
tional 

to 
steam 

Total 
includ- 
ing 
revised 
"spot" 
and 
"spot 
delay," 
minutes 

/urved, 

Tree 
diam- 
eter 
breast 
high, 
inches 

Yarder 
minutes 

Swing 
minutes 

Yarder 
minutes 

Swing 
minutes 

sawing, 
minutes 

18 
20 
22 
24 
26 
28 
30 

.300 
.400 
.520 
.700 
.900 
1.150 
1.450 

9.94 
9.99 
10.08 
10.26 
10.45 
10.76 
11.15 

9.91 
10.05 
10.25 
10.58 
10.93 
11.37 
12.00 

7.77 
7.91 
8.11 
8.44 
8.79 
9.23 
9.86 

5.70 
6.90 
8.20 
10.00 
11.50 
13.20 
15.00 

.63 
.76 
.91 
1.10 
1.27 
1.46 
1.66 

8.40 
8.67 
9.02 
9.54 
10.06 
10.69 
11.52 

33.1 
25.0 
20.8 
14.7 
11.6 
9.3 
7.7 

28.0 
21.7 
17.4 
13.6 
11.2 
9.3 
7.9 

33.1 
26.0 
19.7 
15.3 
12.4 
10.7 
9.6 

28.0 
21.7 
17.4 
13.8 
11.6 
10.2 
9.1 

32 

1.040 
.760 

10.63 
10.32 

11.17 
10.70 

9.03 
8.56 

16.70 

1.85 

19.44 

11.6 

10.8 

8.9 

1.800 

20.95 

21.87 

17.59 

8.4 

34 

1.280 
.920 

10.93 
10.47 

11.63 
10.96 

9.49 

8.82 

18.70 

2.06 

20.37 

9.7 

9.3 

8.3 

2.200 

21.40 

22.59 

18.31 

8.0 

36 

1.510 
1.090 

11.25 
10.70 

21.95 

12.13 
11.25 

9.99 
9.11 

20.50 

2.27 

21.37 

8.4 

8.2 

7.9 

2.600 

23.38 

19.10 

7.5 

38 

1.740 
1.260 

11.76 
10.90 

12.66 
11.59 

24.25 

10.52 
9.45 

22.50 

2.49 

22.46 

7.5 

7.5 

7.6 

3.000 

22.66 

19.97 

7.2 

40 

2.000 
1.450 

12.44 
11.08 

23.52 

13.27 
12.00 

11.13 
9.86 

24.40 

2.70 

23.69 

6.8 

6.9 

7.3 

3.450 

25.27 

20.99 

7.0 

42 

2.290 
1.660 

13.29 
11.58 

13.92 
12.48 

26.40 

11.78 
10.34 

26.50 

2.93 

25.05 

6.3 

6.7 

7.0 

3.950 

24.87 

22.12 

6.9 

44 

2.550 
1.850 



4.400 

14.01 
12.04 

14.54 
12.92 

12.40 
10.78 

23.18 

28.50 

3.15 

26.33 

5.9 

6.0 

6.7 

26.05 

27.46 

6.7 

46 

1.770 
1.710 
1.420 

11.83 
11.68 
11.10 

12.73 
12.60 
11.94 

10.59 

10.46 

9.80 

30.50 

3.37 

34.22 

7.1 

7.0 

6.4 

4.900 

34.61 

37.27 

30.85 

6.6 

48 

1.950 
1.890 
1.560 

12.30 
12.14 
11.37 

13.16 
13.03 
12.25 

11.02 
10.89 
10.11 

32.30 

3.57 

35.59 

6.6 

6.6 

6.1 

5.400 

35.81 

38.44 

32.02 

6.5 

Bulletin  371]       the  relative  cost  of  yarding  timber  35 


GENERAL  CONSIDERATIONS  AND  CONCLUSIONS 

Conditions  vary  widely  between  different  lodging  operations  even 
within  a  given  region.  It  is  therefore  futile  to  try  to  prepare  general 
figures  which  are  of  exact  applicability  everywhere.  The  foregoing 
discussion  illustrates,  however,  the  fact  that  analyzed  figures  on 
details  will  often  apply  where  totals  will  not.  The  total  cost  of 
yarding  was  quite  unlike  in  the  three  studies,  yet  both  the  relation 
between  the  costs  for  different  distances  and  that  between  the  costs 
for  different  sizes  were  essentially  the  same.  It  is  for  this  reason,  as 
well  as  to  support  the  conclusions  stated  on  page  3.  that  the  foregoing 
tables  with  their  large  amount  of  detail  have  been  presented.  There 
is  much  information  therein  which  may  prove  of  value  to  lumbermen 
who  are  studying  their  operations  with  a  view  to  increase  efficiency. 
It  would  be  easy,  for  example,  to  construct  from  them  revised  tables 
(similar  to  table  21)  which  would  be  applicable  to  any  hauling 
distance  and  to  trees  of  any  height. 

It  is  of  interest  to  consider  again  the  statement  made  in  Bulletin 
339,  "The  Relative  Cost  of  Making  Logs  from  Small  and  Large 
Timber"  (see  footnote,  page  3)  as  to  the  probable  causes  which 
underlie  the  high  costs  per  m.b.m.  associated  with  the  yarding  of 
small  trees.     These  are  three  in  number,  as  follows: 

(1)  The  Scribner  log  rule  (and  also  the  Spaulding)  is  ultra- 
conservative  in  the  values  assigned  to  small  logs;  if  an  over-run  of 
6  per  cent  is  to  be  expected  from  48-inch  trees,  as  much  as  24  per  cent 
should  be  obtained  from  3  8-inch  trees.  Were  the  results  of  table  1 
expressed  in  terms  of  lumber  tally  instead  of  in  terms  of  log  scale, 
therefore,  the  average  cost  of  yarding  logs  from  the  smallest  size  trees 
would  be  only  S1/^  times  instead  of  6%  times  that  of  logs  from  the 
largest. 

(2)  The  yield  in  lumber  per  cubic  foot  of  actual  volume  is  smaller 
for  small  trees  than  for  large  on  account  of  the  greater  percentage  of 
waste  involved  in  sawing  lumber  therefrom.  Costs  per  cubic  foot  of 
volume  would  be  less  unfavorable  to  the  small  sizes  and  on  this  basis 
the  ratio  between  costs  for  18-inch  and  48-inch  trees  is  further  reduced 
to  3.8  to  1.  This  fact  is  of  little  significance,  however,  in  connection 
with  present  day  manufacturing  methods,  though  of  course  of  possible 
future  importance. 

(3)  The  remaining  important  factor  is  the  large  amount  of  time 
which  must  be  spent  on  every  tree  and  on  every  log  regardless  of  its 


36  UNIVERSITY   OF    CALIFORNIA — EXPERIMENT   STATION 

size  and  which  in  the  case  of  the  small  trees  must  be  charged  against 
the  small  volume  obtainable. 

In  conclusion  it  should  be  stated  that  the  foregoing  figures  were 
not  collected  with  the  idea  of  proving  any  theory.  They  were  gathered 
in  connection  with  a  general  investigation  of  the  factors  affecting  the 
cost  of  logging.  These  factors  are  many  but  from  the  commencement 
of  the  compilation  of  the  data  it  was  evident  that  tree  size  was  of 
prime  importance  in  almost  every  phase  of  a  logging  operation. 
Studies  by  other  investigators13  indicate  that  a  similar  condition 
prevails  in  the  sawmill  and  it  is  well  known  that  the  quality  of  the 
lumber  produced  from  small  trees  is  inferior.14 

There  are  considerable  differences  between  the  practices  of  lumber 
operators  in  removing  or  leaving  the  smaller  trees  encountered.  Some 
log  practically  every  tree  large  enough  to  produce  a  saw  log,  while 
others  leave  standing  everything  below  a  rather  flexible  diameter 
limit.  Within  recent  years  the  tendency  in  California  has  been  toward 
closer  and  closer  utilization  in  this  respect,  although  little  exact 
information  as  to  its  desirability  has  been  available.  While  the 
present  study  is  perhaps  not  conclusive,  since  only  certain  phases  of 
lumber  manufacture  have  been  investigated,  the  figures  presented 
herewith  suggest  forcibly  that  the  present  policy  has  been  carried  too 
far  and  that  a  more  conservative  plan  would  be  financially  profitable. 


1  s  Show,  S.  B.,  "An  Analysis  of  the  Cost  of  Sawing  Logs,"  Timberman, 
July,  1922,  page  40. 

I*  Berry,  Swift,  "A  Study  of  the  Grades  of  Lumber  Produced  from  Cali- 
fornia Pine,  Fir  and  Cedar,"  Lumberman,  March,  1918,  pages  36  and  37,  and 
April,  1918,  pages  39  and  40. 


